What Lens are you using for Wildlife?

[Inukshuk]

I'm getting more into wildlife and would like to know what glass you are all using to get the job done.
Myself I'm testing with my 70-200 f/2.8 with 1.4x-2x converters for now. Just learning how to get the best out of this set-up. But recently I've been looking at the new Sigma 150-500mm. Would be nice but don't know yet if I'll make the jump or not.

 

[Headshotzx]

The longer the focal length the better I would assume. I'm no wildlife photographer, but here goes:

You'd want longer focal lengths, and primes fair much better i believe.

You can get a 300mm f/4IS or a 400mm f/5.6L for around (or under) S$2k.

300mm has IS, but is a bit short. 400mm has the focal length, but has no IS and has a small max aperture.

Following that, you might want to get a 400mm f/4 DO IS if you really need the f/4 and IS over the 400mm f/5.6L. Note the price increase (few thousand bucks). If you need more reach, 500mm f/4IS (or the 500 f/4.5 without IS) for something close to like 8-10k. Painful investments.

A good tripod would do you well if you're really planning on photographing wildlife. Good knowledge of your subjects would be of great help also.

Hope this helps =)

EDIT: The above is assuming you shoot Canon. If you shoot on any other mounts, just take note of the specs I guess.