A friend of mine has a nasty Eldar 400pt list that put a stop to my 400pt Drop Troop Guard rampage (we were both undefeated and fighting for 1st place very dramatic
). Basically what he takes is a squad of Dire Avengers with no heavy weapons and a Exarch with a power weapon, a squad of Spiders with Exarch w/dual spinaret? guns(sorry i dont have an Eldar Codex!) and 3 war walkers with scatter lasers. The Avengers die pretty quick. But the spiders are a pain in the ass when they are popping up all over the board and laying down a pile of S6 shots only to warp away during the Assault phase! In the end it came down to his Warwalkers and my Sentinels in Close Combat which I sadly lost
All in all it was a good game and a very formidable list to play against.
Hope this helps!