I'm big into handguns, so I'd say go with a Sig P226 Combat with a threaded barrel
But, if you're looking at crossbows, check out the PSE Tac 15 (let it be known, for bows, I'm a Hoyt person thru and thru). A guy I work with has one, fits on top of an AR lower. He says it's just one nasty hunting tool.
"Have you paid your dues, Jack? Yessir the check is in the mail" - Jack Burton, Big Trouble in Little China
"Catch me in five minutes, I'll smell like hard liquor" - Al Bundy
Inducted Blade 2010- Ham67