I have shot rabbits commercially with all manner of air rifle...the best system is the air bottle rifles and use a manual track pump to fill them rather than the "scuba" bottle approach...it is cheaper and always able to be used...fixing the pump is easier as well than fixing a pump up rifle...plus with an air bottle rifle you get a magazine system and a quick second shot...just like a bolt action rifle...which is invaluable for putting game on the table...you can take multiple rabbits with this system. Also you can buy a few spare air bottles for the rifle and load these up and shoot all night if you want....at 50-60 rabbits a night you can soon pay for the rifle and scope.
You can also regulate the power on the rifle so it shoots at the ideal velocity for your needs.
Remember to budget for a good scope....it is worth it in the end. <img src="/ubbthreads/images/graemlins/thumbup.gif" alt="" />