1) A term generally used in first person shooters (FPS) games for a team who is secretly takes advantage or gets the upper hand by ambushing the other team.
2) Devious and secretive about your intentions or motives: relating to or from the point of view of person trying to avoid attention.
3) Out of the ordinary to go somewhere secretly, or to take someone or something somewhere secretly.
4) Catchphrase for a surprise attack.
Oh!, their (or he/she's) playing a little sneaky sneak.