First roll I make in a new Play by Forum game is a Perception roll when I walk into the orphanage where I have to provide security for a 'winter solstice festival'. Not because the GM asked for it, but just to see if I notice anything that might be noticed. Basically, a throw-away roll.
And it comes up as a natural 20.
I guarantee you that if a roll comes up that I absolutely have to make, then I'll miss it.