Small Rooms
The best conversations I've had about hard problems happened in small rooms — sometimes literally, sometimes just two people and a shared doc. Add a third person and the dynamic changes. Add ten and it changes completely: someone starts performing, someone else starts defending a position they don't actually hold, and the actual problem quietly leaves the room.
Big groups are good at ratifying decisions and bad at making them. If you need a real answer to a real question, you're usually better off finding the two or three people who understand it best and letting the rest of the organization review the outcome, rather than trying to think together in a room of fifteen.
This scales down further than people expect. Sometimes the smallest room that produces a good answer has exactly one person in it.