IMHO, very few spring piston or pneumatic pump air pistols meet the power levels needed for hunting.
My error to your reply: I meant pre charge pneumatic rifles. I don't know of any pump pneumatic rifles or pistols that will humanely kill varmints as large as rabbits from beyond 20 + yards unless an exceptional head/ spine shot is attainable.
There are a few spring rifles that have foot pound ranges with in the 24-28 foot pound range which is sufficient for a humane kill within 50 yards:-
Beeman, Bejamin Nitro, Gamo Falcon Hunter,RWS and quite a few more.
pre-charged pneumatics are the upper end of power.