Nitro, Purdey, Westley, buckshot, gunner, Sig, trigger... or maybe name him after your favorite drink or beer.
Guinness, Foster, Pabst, Busch, Dragon, Hacker, Moose.
Tequila, Gimlet, Joker, Mojito, Blinker.
Or maybe after your favorite ammo: Olin, Jamison, Cor-bon, Norma, Lapua, Nosler, Ramshot, Varget.
Maybe after your favorite cartridge: Lott, Ackley, Swift, Ribgy.
How about your favorite author: Boddington, Massad, Cooper, Elmer, Skeeter, O'conner, Capstick.
Or maybe a favorite movie character. We used to breed and raise border collies. If the the client spoke for a pup before we had to send the registration papers in, we would let them name the dog. If not, they all received names from characters in John Wayne movies: Duke, Chance, Maggie, Quirt, Jake.
Maybe your favorite movie character. Josey, Cisco, Hopalong, Quigly, Hannibal.
Or maybe your favorite city: Nash(ville), Vegas, Berlin, Dublin, Cork, Reno.
With a little imagination you could name your dog with an "original" that most people wont have already used.
Good luck !