For North American game,..from feral hogs to Moose to Bear, my answer is always the same.
30-06 by.... whoever. Remington, Savage, Winchester, etc.
Everyone makes a 30-06, and you can always find ammo for it.
Ammo comes in a variety of loads for light shooting to big game.

I was at WallyWorld today and they had a Savage 30-06 for around $360, rifle and scope. Good gun, good price.
http://www.walmart.com/catalog/product.do?product_id=2684985

Sorry, Ijust reread your post and you stated you wanted to hunt turkey also.
A Shotgun's the way to go for that.
A bunch of options there. I'm not a big shotgun guy, I've had the sameRemington for 23 years now, so maybe someone else can shed some light on that.