Mobile Gambling Game
In the game Ingress, you go around in real life and capture "portals" that are landmarks. You can't do this alone so you join a team (there are two) and compete against the other team.
2. Pokemon Go (or any other game where you catch Pokemon)
You go around and try to catch rare pokemon.
Every day at noon, there's a live trivia game where people answer questions to win money. People have formed teams and have their own chat groups.
4. Trivia games on FB Live or TikTok or wherever else they happen
People form teams and compete against each other answering trivia questions.
5. Chess / Checkmate
A social media platform where people play chess with each other. You can set up matches between players or just play casually whenever you want. The site would charge users to watch high-level players play each other for money or for free on lower levels.
6. Poker tournaments with real money prizes every night!
People would pay to enter tournaments of different stakes ($10 buy-in tournaments, $100 buy-in tournaments, etc). The site would take a cut of the tournament entry fees but make it worth it by having lots of high stakes tournaments every night so there's always action happening on the site.