If it's actually a fight, then not a gun. It's not a fight if he doesn't have one, and if he does, I can easily die even if I kill him.
I'd think a big knife/machete/sword would work, but what if I'm crap with them and I get disarmed? I definitely can't fight off someone with those.
So maybe something harder to lose, like a knuckle duster? Although then I could just be outfought.