Synonyms for Sneaker (same or very similar meaning)
WordNet sense 1 (someone acting as an informer or decoy for the police):
canary, fink, snitch, sneak, snitcher, stoolie, stoolpigeon, stool pigeonWordNet sense 2 (a canvas shoe with a pliable rubber sole):
gym shoe, tennis shoeFrom the ODE community, based on WordNetadd/edit