At first I thought you might have cards with just numbers and, as rolls are made for combat/damage, players would check them off, achieving a cool in-game effect when they bingo. But, that seems like it's doing the opposite of what we really want. I want players excited and leery about the battle they're in not distracted by the layer on top of it that the bingo would be. Maybe this could work for huge battles
Dungeon Bingo Leveling
Now I'm thinking maybe it would work more closely to the original car bingo concept. So you have a card with various dungeony things and you cross them off as you encounter them (Hey, Googling shows Risus Monkey's player used the term in a similar way, hah). When you get a bingo what happens? I'm not sure. This sounds remarkably like Achievement Based Level Progression. Hah, maybe this is the way DM and players could recordkeep as well as a way players could have an idea of things they might do without a strict hierarchy of them, because Bob might need X for a bingo, but Jill needs Y. Of course that brings out a flaw, the whole point of bingo is one person gets it before the others and that it's random. So if you did advancement this way one random player would go up before everyone else. Seems suboptimal. Another problem that comes to mind is that drawing out the filling of the bingo card over several sessions seems like it would ruin any exciting tension that might build.
[Ok, several hours and a road trip later] maybe you could use the cards for NPC bingo. You make cards with vague things like:
- is an orphan
- was robbed in the last month
- despises a neighbor
- has an unrequited love
- complains about an ailment
The big unanswered question for me is what is the bingo prize? Free rumors? A secret about an important NPC or local spot? Maybe a discount on lodging and equipment for the day? Or, I suppose the most straightforward would just be XP.
Update: The bingo might be a little too clunky and gimicky to be useful, but I thought of a place where it could be quite fun. At a convention give bingo cards for each game table. Have all the bad stuff that can happen to a party (TPK, death by poison, death by trap) and for each group that gets a bingo, every player gets a consolation prize.