The Termagaunts equipped with fleshboarers are my second choice. With a strength of 4 in shooting, they can harm nearly every infantry the opponent can field and even most tanks when they get to their rear armor. On the other side they cost a mere 6 points which makes them expandable to say the least.
They performed so well over the first year of playing nids that I now have 60 of them. For the sake of sanity I painted three squads of 20 with different colormarkings.
22 hours ago