THere are a lot of great turkey guns and you may even be able to use one you have. The right choke tube can turn an upland gun into a turkey gun in about 5 seconds.
As far as what I like. My favorite is an 870 Super Mag. But again most guns can be made into a good turkey gun with the right choke tube.
Another great option is to bow hunt them if you are a bow hunter. A little harder but a lot of fun