Rock Paper Scissors

Rock Paper Scissors is listed here under Multiplayer. There is no launcher and no install between you and it. Taps and swipes are the whole vocabulary — a phone plays it best. Listed under 2 player, arcade, games, kid, multiplayer.

It is drawn for a tall screen, so it fills a phone held upright rather than a wide monitor. It costs nothing and asks for nothing: no registration, no download, no launcher.