Responses clearly show the best choice depends on what threat you might encounter, with the biggest being a griz of some flavor, and perhaps the most dangerous being a man intending harm. Seems a crazy fishing endeavor, or at least a shame, where truly dangerous people must be considered, but it is what it is.
I'd take plinking out of the equation. YMMV, but if I'm fishing, I'm fishing. But if small game is a consideration, then plinking of a sort is back on the table.
If snakes are the only consideration, then a question is are you shooting at any "bad" snakes you see, or only those that somehow wind up too close for comfort. If the latter, I'd seriously consider a shot load of some kind.
If not fishing, but hunting, then is your primary a rifle or shotgun, how big, yada, yada, yada.
Edit to add: The OP was too broad a question, but perhaps he was looking for things to consider in addition to guns to consider.
Last edited by GunDoc7; 09/15/19.
