I think the effect would be lessened if you pulled a hamster out of your pocket and someone saw you. If you work in a pet store, have a cage with those in it and casually take one out and gnaw on it while you're talking to an annoying customer.
It might work better if you put one on a table.. nudged your friend and go 'is..is that a hamster?" then 'sneak' up on it and SMASH it flat with a mighty yell. Then shove it into your mouth to finalize your victory. or bite it in half and throw it at them if you're feeling extra crazy.