I managed to pull off 37 mph on my MTB on a surprisingly puny hill south of here. The wind conditions were just right and there weren't any cars so I just went for it. My biggest fear was foot slip since I don't use clips or cages but everything worked out ok.
Once I did 32 on a flat stretch during a winter weather advisory...the snow had not made it here yet but the winds out ahead of that system were INCREDIBLE. Now when the weather gets really windy I start thinking which direction to head off in so that I can challenge my record.

Oh and I know this doesn't count, but the last cyclometer I had got moisture in it (get what you pay for) and everytime you got up past 20mph or so it would suddenly go berzerk and start flashing 99s and 100s and stuff. Either that or I inadvertently rode thru a wrinkle in time.