what are yours? could be fluff wise, could be rules based/competitive. here are mine in no particular order:
SW 5th edition (duh)
catachan 3rd edition (had sooooo much fun playing with this)
lost and the damned (never played but my buddy did, it was great)
chaos 3rd edition (one of the best ever, the way they split up the factions)
tyranids 4th edition (was great, reaaalllyyy got worse with fifth, both fluff and rules wise)