How much money do you got?
How much do you want to spend?
How fancy do you want to be?
In the olden days my answer would be to get a military surplus German WW2 8mmx57mm mauser bolt action rifle...
Mine cost 80 bucks in 1976.
Nowadays the going thing is a military surplus Russian WW2 7.62mmx54mm mosin nagant bolt action rifle...
They are available for about 99 bucks.
Both of these guns are about as powerful as the tried and true 30.06.
Thats plenty for bear, deer, elk and Zombies!