Games on Demand is a gaming event held at lots of conventions, dedicated to setting up tabletop RPGs (in the vein of D&D) for pickup groups. No reservation required, no planning needed, no familiarity required, just swing on by on the hour and see what games are going to be running.
I first played Psi*Run, learning it was like X-men meets I Am Number Four. Each of our runners had superpowers of our choosing, and were being chased by some technologically superior military entity.
I created a runner called Shaper, who could absorb and reform material with his hands a la Fullmetal Alchemist. As the dice were rolled and the numbers allocated toward power strength, power safety, deterring the chasers and learning more about your past, I made my powers regularly go wonky. We stayed away from the chasers, but opening a gap to enter a building reformed too much material and the building trembled, setting off all the alarms.
I played alongside some DMs from the Wizards of the Coast booth. We made up the story along the way, and had each other answer the questions we laid out about our pasts, like “Why can’t I shape the handcuffs I woke up with?”