Use pepperoni. Its fibrous texture means the mouse has to tug harder to pull it loose from the trigger, making the trap more likely to go off.
Besides, the mouse dies happier.
On no account use soy cheese. No creature's last thought should be "What the hell is this?"
LOL!
They like jellybeans, too. But if you live-trap like I did, be warned - after eating a jellybean the size of his head, that mouse is gonna be wired.