I use the standard D style Sanke tapper. Fits most domestic kegs, including Sam Adams. See chart here:
http://www.beveragefactory.com/draftbeer/couplers/american/FAQ_COMP.shtml

Beer line comes out the top, gas line on the side.

I've only bought an import keg once, and that required a different tap -- too much hassle, so I don't buy import kegs anymore.

Corny keg I use the same as you - the ball locks. Wish they made an in-line quick diconnect fittings so changing from my Sanke to ball-locks was easier.