Just about any rifle which is reliable and you have sighted in so that you know where it will hit.
It should be reasonably accurate which just about all new rifles are.
If it has a scope, make sure it is really well mounted. I once had the scope on a Thompson Center Contender fall off during a match. I sure thought it was on good but it wasn’t.
Just have a good supply of ammo too. If you have enough ammo and can shoot the rifle well, then caliber is not important.
Even a .22 or .22 magnum is better than nothing.
Oh, yes, that one too. High Standard two shot .22 magnum derringer (no exposed hammer) for discreet occasions when it REALLY has to hurt and/or cause severe damage. And, the double-barreled shotgun is sawed off, I forgot to mention.