Garth Ennis' A Train Called Love

Thrill-seeking Valerie's been getting dirty phone calls, but when she goes to take revenge on the pervert responsible, she meets Myles, the man of her dreams. Of course, Myles is a gentlemanly hitman who just executed said pervert, and while that's a turn-on for Valerie, she unwittingly becomes a target for several unsavory types...