With Cata here there are tons of new achievements and killing 50k critters is one of them. Your guild can get the armadillo pet once exalted with the guild. I was flying over Uldum doing quests and I came across a patch of sheep. There must have been 20 or more and there were 2 groups of 10 right by each other. So I thought I would stop by and aoe the groups for an easy 20 critter kills for the guild. I went ahead and aoe'd the sheep and they immediately spawned back. Needless to say I stood there and did this for 30 mins and got 50k critter kills. I got up to about 61k then Blizzard did a instant hotfix and no more instant spawns on the sheeps. Sorry i broke it guys
This hotfix was done like 2 days ago..... There is still a place in eastern plaguelands that has a TON of bugs that can be killed for the achieve.