The Tau have very interesting minis. And though the official Tau miniature for inq54 is a diplomat (the water caste envoy), Papah miniatures designed and released what is arguably the most slick unofficial inq54 miniature ever produced for sale, the alien commander.
A few Air Caste figures have been made by fans (not sure who made them though?). I got one via a member of the conclave. The other I got from ebay [Ed: the resin cast is very poor.i need to stop faffing about and fill in all the pockmarks].
Back to the alien commander. This is a beautiful sculpt and it seems to have captured the imagination of many a great painter [Ed: just check google for some amazing paint jobs].
The alien commander kit had many optional heads and arms and weaponry. Version 1.0 was in white metal and came with a scenic base (a disemboweled imperial guardsman). Version 2.0 was cast in white metal and resin. There were 7 heads to choose from (i think you paid a set price per head? And there were 4 different arm sets, and again you chose which arm set you wanted.
Other than the Tau themselves, a Kroot was also official released. This mini is also great, and it is huge! I’m not sure whether the impressive height of the Kroot is faithfully reproduced in 28mm 40k, but in inquisitor, this mini is so big and towers over others. The Kroot Mercenary is an okay sculpt, but the Kroot expansion set to convert the mercenary into a Kroot warrior is pure genius.
Still on the wish list is a great knarloc by forgeworld. I owned one over 10 years ago and it was a very nice mini. But i sold it and the mini is now long out of print now. But it would be perfect in size as a lesser knarloc.