[roundest]

When he pulls the knife, tell him you'll fight him but you need to go over the rules first. When he says there are no rules in a knife fight, kick him in the balls as hard as you can and say, "Well, if there aint' going to be any rules, let's get the fight started. Someone count. 1,2,3 go." After your new girlfriend yells out, "1,2,3, go!", knock him out with a doublefisted roundhouse punch.