There are accepted ways for one to communicate to a salesperson that one is busy taking advantage of the product demo and would rather not have a sales pitch interfere with his gaming experience:
"Excuse me, sir..."<br>"Can't talk. Smashing."
"Sir, pardon me."<br>"Look, I'll buy something if you get on player 2 and let me whip your butt for a half hour. Take the Ice Climbers -- they suck."
"Are you interested in in-store credit?"<br>"Sure. The people at the debt restructuring agency say I shouldn't get any more credit cards, but this is different, right?"
"Sir-"<br>"If you can tell me why I got points off for 'shameful fall,' then I'll listen to what you have to say."
"Let me tell you about our warantee..."<br>"Take that, Ganondorf! Yeah, suck up my ghetto-pika-tabulousness! What were you saying?"
If they try to kick you out, claim you're a "mystery shoppper." This will put them on their guard, because mystery shoppers usually write down all infractions and rat out staffers whom they don't like.
*Invites everyone over to my place for some distraction-free Smash Brothers Melee*
But beware, practice has made me deadly.
...Another strategy for playing in the store would be the diversion method. Hire an accomplice to do something in another part of the store that'll distract and occupy most of the staff - like making a huge scene, or setting a small fire.
Bring lots of disguises, and trade places every two hours.
I have no appreciable gaming skills. Progress Quest is about as capable as I get.
And it's always good to have someone start ransacking the Martha Stewart goods display first, screaming something like "destroy the idols of the demon godddess," because then the staff is too busy saving the bed linens to care about how long you play Smash Brothers.