80s and 90s kids will remember this, and it's making a comeback as a novelty item. No storyline, no visual and auditory stimuli, just a simple challenge to hook all the rings in the posts (extra points for achieving color patterns), so it's up to your imagination to fill in the rest. Real randomness, too, not subject to some random number generator. A real zen gaming experience.

Pros: no batteries needed. Cons: risk of water spillage, occasional refills needed.