44 Mag, it would probably be the most effective without having to try to load it up and the over the counter options are very good. 45LC is good too, and can be loaded up to 44 mag levels, but like I said, it has to be loaded up. Both throw a huge chunk of lead though. The 357 Magnum would be another attractive option, just because it is so easy to shoot well and you also have the option with it of using 38 special in it to shoot it cheaper.