Get out my top hat and cane and start singing:
“Hello my baby
Hello my honey
Hello my ragtime gal”
Could I use his gun as a prop? 
Though I suppose that would run afoul of the ‘no chance of disarming him’ clause.
My act is snorting Kim Jong Il’s toupee through my left nostril. Sir, if you’d be so good as to go get my prop…
My one prop is a SWAT team riot shield and my act is broken field running. Most people can’t hit the broad side of a stationary barn with a pistol, I’m willing to take my chances.
One of two options:
A) Whip out my transvestite costume and prance around to Sweet Transvestite. He’ll either be so frightened he’ll run away or I’ll transfix him with my macho/mince routine and be able to take the gun.
Or
B) Do my rendition of the Animaniacs Presidents of the United States song. People usually like that one. I’m not even an American. Go figure.
Well I’d start by telling him The Story of the Merchant and the Jinni.
Realistically? I would probably flip out and start crying and begging. I have this crazy phobia at being shot at.
“Ooo can I do* Danny Boy*? No… Loch Lomond! No… I Did It My Way! No… Diamonds Are A Girls Best Friend!… Candyman! … Moulin Rouge!…
Tell you what, can we just come back tomorrow and get a backing group and big band?"
My prop would be a guitar and I would sing to him. He would have to have a high tolerance for me forgetting songs halfway through and strumming aimlessly while I try to remember. Funny, I was only thinking this morning that if I don’t start playing my guitars again soon they’re going to put themselves on Ebay out of boredom.
Hmm. I think my prop would either be a piano, in which case I could sing and/or play the few pieces I know by heart, or lots of beer, in which case I could get drunk and start talking nonsense, which I’m told can be quite amusing (probably only to my close friends, though). Neither of these is likely to work for long, so perhaps I’d go for the latter, because by the time I get shot I might be drunk enough for it not to hurt as much.
Some great one-liners upthread, by the way - you guys are going to have no problems.
I always knew my tap-dancing skills would come in handy sooner or later.
The only entertaining skill I have is the ability to perform card tricks.
For my next trick, I’ll need to lock a volunteer from the audience inside this box. You, sir, with the gun…
Get shot. I have zero talents.
I’ve just spent the last week teaching myself to play the guitar, so I’ll play the one punk song I’ve learned. Oh, he’ll still shoot me, I just want death to come quickly. It’ll also make my last moments as terrible for him as for me (not to mention the neighbours).
Surprised no one has mentioned russian roulette yet, deer hunter style.
Declan
Jokes. I got jokes.
Ever heard the moth joke? I’d tell that one. People either love it or hate it, so you’ll know in a few minutes whether you’re going to live or die, and avoid all the suspense.
I play guitar and sing, and I have plenty of material.
So that means I can’t perform my ‘juggling unfired bullets’ trick?
yeah you’d die