NEANDERTHAL POETRY
There are many ways to play this game. The main challenge is to communicate a concept by only using one-syllable words.
Variations:
One player might whisper a concept to another play, who then must get the rest of the group to guess the message.
Two players can attempt to carry on a conversation using only one-syllable words until one person messes up. In a larger group, a player is out when they use a longer word, until one is left victorious.
One player can decide to play the game without telling the others, speaking in only one-syllable words until others notice.
This is a no-supplies interpretation of the incredible game Poetry for Neanderthals which comes with an inflatable bat for head-bopping whenever a player uses too long of a word.