First off, I would just like to say that equipping a crisis suit is something even tau veterans tend to bicker about, so I will try to stick to facts as much as possible, but if anything opinionated slips in, that is how I play MY suits at MY local store against MY opponents, and may not necessarily be the best for your situation.
Now, the weapons available to our suits are as follows:
-Airbursting Fragmentation Projector
This is one of the few large blast templates we get out side of apocalypse. Basically, a pie plate barrage with the Ignores Cover special rule, and the stats of a bolter. 0-1 for your army, but really comes in handy against IG infantry swarms and green tides. Good choice for a bodyguard, if you use them
-Burst Cannon
AP5 heavy bolter with about half the range, there are really only two things about it that are appealing: it's got good dakka, and it's cheap. Better than in 5th, as it can cause damage to transports/back armour tanks now.
-Cyclic Ion Blaster
You thought the burst cannon had dakka? You ain't see dakka. Comes with an unholy 5 shots a turn, but suffers from mediocre range and low strength. The good thing is it has a slightly weaker version of rending on it so it can sometimes pierce marine armour, and already penetrated anything less regardless. 0-1, like the AFP. Only suitable for high BS suits (usually a Shas'el with a Targeting Array).
-Flamer
Same as all the other races flamers. You'd think if guardmen could carry heavy flamers, that crisis suits could too but I guess not. Dirt cheap though, so sometimes used twin-linked on suicide suits (for fun) or to fill a third hardpoint, being the second cheapest option right behind the black sun filter.
-Fusion Blaster
Standard melta, good for killing tanks when you get real close, but you generally shouldn't get 'real close' with tau so...yeah. Pretty average price. If you are the kind of person willing to sacrifice their suits for the greater good...and the hope of exploding a land raider...then they can make excellent use of the XV8's inherent mobility and deepstrike capabilities, especially paired with a skyshield/pathfinders/tetras.
-Missile Pod
This weapon is one of the gems of the battlesuit armoury. It is an autocannon, a beautiful, beautiful autocannon. The longest ranged weapon battlesuits can use (not counting broadsides...), they are often used as backfield weapons. Not too expensive either. In my lists, I rarely have a suit without one, usually only one or two per game. Pairs well with every weapon in the armoury, and can be twin-linked, like all the others.
-Plasma Rifle
A nifty weapon, it was a staple in most lists in 5th edition, though now it's status as 'ubiquitous crisis suit weapon' is being quickly usurped by the missile pod, at least in the stores I visit (4 of them). It's basically a plasma gun, -1 strength and without the Gets Hot! special rule. You can see how that would be useful. The problem is it's expensive, and only gets one shot at 12-24", and none beyond that. Good against marines, generally not worth it against non marine armies though (high strength low ap weapon usually don't do much to a horde of gaunts). AP2 got better though.
Now, onto support systems:
Only gonna list those pertinent to crisis suits, which also happen to not have been discarded by GW (C&C node, target lock).
-Blacksun Filter
By far the cheapest thing you can put on a crisis suit. Grants Night Vision. Better than in 5th. If you have no idea how to fill up that last hardpoint, it's a pretty safe investment.
-Drones controller
Lets you take shield, gun and marker drones. Shield is probably the best of them, though it is not essential for standard crisis suits as it bumps up their cost significantly.
-Multi-tracker
Awesome equipment, super cheap, fills a hardpoint and lets you fire two weapon, this is one of the major factors that make crisis suits awesome. This wargear is one of the most important entries in our codex, without a doubt.
-Positional Relay
A lot worse in 6th than it was in 5th. It is 0-1, and it let's you bring in reserves on 2+, regardless of what it otherwise would be, and makes only 1 unit roll for reserves each turn, so you can keep your army in reserve longer, and bring a unit in with a fair degree of precision. Now that turn 3 reserves are 2+, and turn four is auto, this really isn't that great anymore.
-Shield Generator
Enormously expensive 4+ invulnerable save. The only time I would recommend it would be on a suicide suit, though I wouldn't recommend the suicide suit in the first place, or on a Shield'O (we'll get to that later).
-Targeting Array
Useful for any suit with access to the armoury, and by extension, the hard-wired multi-tracker. +1 BS, it's kind of expensive but I guess it's worth it if you keep your suits safe.
-Vectored Retro Thrusters
You can only get it on a lone suit or an independant character, and it's 0-1. It gives you hit and run. Pretty bad in 5th, your lone suit probably didn't survive the combat. Now, however, it is good. Hit-and-run is conferred to the unit in 6th. You can have your 30 kroot + blob benefit from hit-and-run. You can have farsight and the seven (or eight, while using this) samurais have hit-and-run. You can confer it to a SM or Eldar unit too. Could be interesting. Maybe have a cheap shas'el flying around pulling tau out of combat, just to see your opponents reaction.
And Finally, on to wargear:
-Bonding knife
A decent piece of wargear if you have spare points, it used to let the unit regroup when under 50% strength. Now, in the new edition, it's not quite as essential as in 5th. Now it makes them regroup at their unmodified leadership value. I guess it could come in handy with 3 suits and two drones, but really it's not such an issue. One way I can see it helping, however, is if your opponent has battle psykers and uses weaken resolve, it won't affect their regroup. Really only useful for Farsight suit, but they get them for free anyways sooo...
-Ejection System
If your commander/lone suit loses his last wound to a shooting attack that does NOT cause instant death (when does that happen?), he gets to eject. You basically have a firewarrior, with a pistol and no armour who keeps the Ld, BS and WS of the suit. Pretty expensive, pretty situational, 0-1. Not fantastic, but on your commander, if he is a warlord, and against dakka armies like IG or Orks, it could work. If it denies your opponent two VP that's great. Also, you can always throw the pilot on to a fire warrior unit for Ld9/10.
-Failsafe detonator
0-1. It is okay on large units of suits (Farsight, stealthsuits). Basically, once you've lost an assault and fall back, your enemy does not get to launch a sweeping advance. The suit equipped with the FSD stays where it is. You centre the large blast marker on it, no scatter, and all the enemies under it take a S8 hit. Might kill a space marine or two, and it will likely eat lots of ork boyz/guardsmen/gaunt, but that's not the point. The point is your other suits escape automatically. Obviously best when it goes off during the opponent's assault phase. The reason you only want it on big units is that you will probably lose the assault by more than just one wound, and the FSD would claim another 1-2 wounds, as the suit using it dies. So you may end up wasting it, with only the FSD suit surviving the assault.
-Iridium armour
2+ armour save in exchange for cutting your jet pack move in half (swapping 2D6 for D6). Pretty expensive too. 0-1. Only really worth taking on a shield'O, and only if he takes shield drones, which inherit the 2+ save.
-Hard-Wired systems
Blacksun Filter, Multi-tracker and drone controller, same points costs, but don't occupy a hardpoint.
-Stimulant injector.
FNP. Not too expensive. 0-1.
Configuartions:
Most crisis suit configurations combine a multi-tracker and two weapons, so we'll look at these first.
There are a huge number of combinations you can make with crisis suit weaponry, but a few of the most common are:
PR+MP+MT (Fireknife)
This suit is good at taking on almost all types of infantry, due to high strength, low ap, high RoF weaponry. Also good at wrecking transports. Pretty expensive though, and needs to be 12" away for max firepower.
PR+FB+MT (Helios)
This configuration is usually used either for anti-armour, or anti terminator duty. Just as expensive as the fireknife, even shorter range. Often uses deepstrike.
MP+BC+MT (Firestorm)
A good suit for anti-infantry due to having the highest rate of fire a crisis suit can get without the CIB, can also wreck transports pretty handily. The high ap is a bit of an issue against terminators and marines, but marines are usually in cover anyways and terminators have an invul save so it's not a big deal. Really cheap, at only 50 points.
MP+FB+MT (Fireforge)
Didn't see a whole lot of this one until recently, it is probably the best crisis suit configuration for destroying vehicles. Having two S7 shots that reach across most of the board and a melta weapon too, being able to fire both in the same turn? Cheaper than the Fireknife, more expensive than the firestorm.
Those are just a few examples of the more commonly used crisis configs with multi-trackers, there are literally dozens of possibilities though so bear than in mind.
Now, twin-linked weapon suits. These generally fill the third hard-point with either a targeting array, flamer or blacksun filter, though you can really put anything there, especially on a suit with access to the armoury.
Twin-linked MP (Deathrain)
This is possibly the most common crisis suit config nowadays, though the fireknife may still hold that title due to being a bit more versatile. Great for long-range transports destruction, for hitting infantry and staying out of range of return fire, or for taking down flyers due to twin-linked, long range, high strength weaponry. I've seen people run them with Targeting Arrays, though I almost always stick with a flamer.
Twin-linked PR (Burning Eye)
This one I have never been fond of. You are twin-linking a single shot at 24", or two at 12". For around the same price as a fireknife. So you can either twin-link 1-2 shots, or have 3-4 per turn. Seems like a waste of a suit to me.
Twin-linked FB (Sun Forge)
This one is for if you want to deepstrike a suicide crisis suit right behind that Land Raider than NEEDS TO DIE. I don't think I would ever run it, but I can see how it would be useful.
Twin-linked Flamer (the Troll suit)
This one doesn't have an actual name, so I will refer to it as the troll suit. Why? Because that huge blob squad of guardsmen, camping in the ruins? They just had a deepstrike troll suit pop up in their face and roast half their guardsmen. Against any horde army, it will probably make it's points back, but never take more than one, and never expect it to survive. Also, don't take it to tournaments. It is only 34 points minimum, so you only need to roast seven guardsmen for it not to have been wasted, but be careful about giving up that free victory point. Could be hilarious paired with a Fail-safe detonator or an ejection system.
Twin-linked BC (Typhoon)
I just made the name up for this configuration. Know why? No one has bothered to name it, or play it for that matter. Don't do it.
A few last notes on configurations:
-Try not to mix suit configurations within a team. It's okay if the team leader has some enhancements to his wargear, but don't mix a suit with a burst cannon and flamer with one who has a fusion blaster and a missile pod. They do completely different things.
-Though it is sometimes tempting, don't take three identical teams of crisis suits. While individual flexibility is important, synergy is even more so. Take specialized teams of suits, and they will excel at their specific task. Something I usually do when I take three teams of suits, one is anti-transport, one is anti-infantry, one is somewhere in between. Another thing I sometimes do is have an anti infantry loadout, a light-vehicle wrecking loadout, and a full-on tank trashing loadout.
-Some people like to take suits with three different weapons. I am not one of them. I think it is a waste, since there is always one weapon staying silent. Don't let that stop you from trying them though.
-Flamers and multi-trackers don't mix. Burst cannons and fusions blaster don't need a multi-tracker. Use common sense.
-One config I didn't list earlier is TL Flamer+Missile pod. Sort of a reverse deathrain. You use it basically like you would a deathrain, except slightly more aggressive. If the enemy attacks you, hit them with three twin-linked flamers. It is also a lot cheaper than a standard deathrain.
