For elk, I would put a bottom line at a .41 mag, but keep within responsible pistol ranges with that, go up as you go up in power. Anything from .41mag to .500mag will treat you well for that type/size of game. There are always exceptions, and many will tell you about their experiences with smaller calibers and bigger game, but for the normal human...
Ruger super blackhawks and super redhawks make really good hunting revolvers, easily scoped, rugged, etc. The Taurus raging bull is also a good one, I have one in .454Casull, a very nice handgun. If you want to spend a lot of money, you can move up to a FA... but that's some major bucks, especially brand new.