A “Multitasking” tag could be useful for a few games, like, well, Multitask, Fire Boy and Water Girl, and some others.
While reading the thread, it came to my mind that a “Cave-flying” tag could fit some games, too. And it would make some Finns happy, I guess. :)
Also, a set of tags like “Scary”, “Creepy”, “Spooky” (and maybe “Eerie”, I’m not sure) to distinguish between games that play with our nerves with various intensity.