I was at the range yesterday and a guy had a Thompson/Center Venture in 308. I've seen them before and thought they were sexy, but after shooting it I'm liking it even more.
Might be worth looking into.
Edit: I should add that you can't go wrong with a WWII rifle like a Mosin Nagant. You can sportify one with an Archangel stock and add a scope. Mosin's are nearly indestructible and still be had fairly cheap, but the best thing about them is the ammo is VERY cheap. Surplus 7.62x54R ammo can still be bought for about 100 bucks for 440 rounds. That's 22/cents per round for a hard hitting round that you can have a lot of fun with or take down just about any game there is.