How can you ask a question like that???[:@]Thats a next to impossible question. It varies but I would say the 6.5x55 Mauser is at or near the top of my list. followed closely by the 45 ACP Ruger and the Taurus Model 65 357 Mag. I hate to think of how many that leaves out.
The old Mauser always hits the target and never hurts the shoulder. What not to love. Also, the critters die very fast.