I'd like to see some Gaunt specialist variants. Reach into the old card game for names and make everything from bioplasma-toting critters to beasts specially evolved to chew through cables and pipes for sabotage purposes. I feel like, considering their original concept as some of the most mutable of Tyranid organisms, they've become a bit restricted to a few basic configurations in ways that, say, Warriors have avoided, and I feel like Kill Team would be an ideal way of getting that adaptability back. A few ideas off the top of my head:
Terrorgaunts- Gaunts armed with rending claws and with evolved graspy legs to allow them to negotiate confined spaces and vertical terrain. Basically cheaper, dumber Genestealers.
Hellgaunts- Gaunts armed with bio-plasma weaponry as "special weapons units", in much the same way as a plasma gunner. Less lethal than an actual plasma gun, but without the risk of exploding.
Pyrogaunts- Scuttling suicide bombs, effectively Hormagaunts with a spore mine grafted to their carapace.
Nightgaunts- Basically Gargoyles that trade their venom and fleshborers for improved melee capacity and, uh, legs!