RE: best .22 ammo for squirrels? rabbits? coons?
 

Some here seem to have the right idea. The 22 is great for what you want to do. I would recommend that you buy a box of 50/100 high velocity from every manufacturer you can get your hands on, initial cost is a bitch but there is not a 22 ever made that doesn't like some particular brand/type , then do some serious evaluation from a good bench rest (keep records).
When you find a combination "YOUR" gun likes, buy the hell out of it making sure you get the same lot number. This will give you an accuracy edge over those that don't adhere to this procedure.
Personally I would recommend "solids" instead of hollow points for any of the game you mentioned even coon. Hollow points open up to quick and lack penetration to get the job done efficiently as possible. You should always be trying for head shots, not always possible I know but that is what you should be doing.
I think the main point of this is, use solids, go for head shots, but above all go through the regime of finding out what your particular firearm likes.

Good luck and have fun.