FWs are awesome if you pick the right targets to fish o'fury with. Then again they're the best unit in the codex! (but i'd say they're underused as most tau players i see at the GT only use 6 as they're compulsory).
Used a sky ray a bit, was useful in assissting dual fish of furies and generally annoying people. Problem was its competing for its slot with another railhead or an ionhead which generally i've found perform better. Alternatively its an awesome choice for a farsight council, making them all BS5 - eek!
I used a piranha for a bit. Only really found a few uses for it. First was using its open topped status for good and assaulting gun drones off it into the end of a squad (though you more than likely need more than one piranha for that). Secondly using its size to an advantage and skimmer blocking with it. That worked quite well. Other than that it usually missed or did nothing!
If you are shooting at MEQ then kroot are more effective, point for point, than fire warriors. 90 points of fire warriors will kill a marine per turn compared to 84 points for kroot.
On top of this kroot infiltrate, move happily through woods, get good cover saves and can actually fight a bit in close combat. I find that their infiltration more than compensates for the shorter range (which isn't really an issue since most FWs are used in fish of fury these days) and they will usually be shooting from turn one.
Kroot really benefit from the tournament environment. It's fun seeing kroot in a wood take on 5 man las/plas squads, power fists, and other anti MEQ stuff you tend to see a lot of in tournaments. I used to keep a tally of the plasma gunners who died shooting at kroot in woods but I lost count.
Kroot are very reliable in close combat. They almost always die, sometimes after inflicting heavy casualties. They used to be ideal for fighting seer councils as they would rapid fire, get a load of attacks, then all get cut to pieces - leaving the seer council to be shot. What you definitely don't want as a tau player is for one of your units to survive a round of shooting, so you can't shoot the attacker. Kroot will either kill everything that attacks them or all die, they will almost never be locked with something tougher than themselves.
Pulse Carbines for Fire Warriors are not often used, but I find they work great. They can either move and pepper enemies, be used as bait, or even tie up an enemy unit in an assault.
Full Gun Drone squads are another thing I rarely see in lists, but using them to Deep Strike or run interference has worked more often then not. They've tied up Termies, blown up Basalisks and Predators, and all sorts of other fun things.
Another often under rated unit is Sniper Drones. While they aren't the best in all comer lists, against MEQ's they are great. A combination of (Possibly) BS 4 and STR 7 AP 3 is awesome. However, they are often pushed aside in favor of Hammerheads or Broadsides.
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