Hats.
It’s kind of a passive game you play whilst doing other things. It’s great for large gatherings, like family holiday parties or birthday parties.
First: Collect some hats. Normal hats, silly hats, giant sombreros and plastic princess tiaras. As each person comes in, give them a hat and tell them to put it on.
After everyone’s arrived, let them all know the rules:
Choose someone to be “it”. You can give them a cool name, like The Grand Poobah of Hat Game Leadership.
At some point during the course of events, the Grand Poobah will remove the hat from his head. Nonchalantly. Don’t mention anything to anyone. Just do it.
Everyone else: When you notice the Grand Poobah has removed his hat, remove yours. Again, don’t spread the word.
The last person dense enough to not have realised that no one else is still wearing their rice-paddy hat, Cleopatra wig, or fedora, has to do a forfeit. The Grand Poobah chooses the forfeit – maybe he has to tell an embarrassing story about himself, or answer a single question truthfully, or perform a silly stunt.
Then the game begins again, with the loser of the first round as the Grand Poobah.