One thing I can't stand as much or more than bikeshedding, are people who will do 'armchair development' in a meeting of many people, raising obstacles, possible solutions, pros/cons, followed by debates and estimations of risk or effort, etc. We could just make a list of items to explore and have two people work it out. Similarly for group guessing figures, when someone could just run a query/report to get an actual number in as much time.