Agario is probably the best and most simple form of PvP game there is known to man. Careful, many hours can go by when playing this. Maybe you are trying to waste time though, this is where you do it.
Throw a paper airplane as far as you can. Upgrade your airplane as you gain money with a handful of awesome upgrades. One of the upgrades unlocks steering so you can steer your paper bro plane into stars and other power-ups!