Right its the time of the day i have to ask this question!...A Hitman Is IN YOUR HOUSE! What are you gonna do?! 8)

Tell him "hi" and ask, "What's that?"
And pretend I don't know what a gun is. Keep him going for a while, and finally ask if I can touch it. At first I gently brush two fingers against it, and he loosens his grip, and then I yank it from his hands and point it at him. Tell him to get out of my house and stay out of other people's too. He runs away and I report him, and give the gun to the police.
What do you think?

I would kick his ass... Then shoot him whiles he on the ground...

Break out my private arsenal and turn him into Swiss cheese. After he has been proliferated we can discuss drop your gun, put your hands up, get down on the floor.