Always found bicycle seats to be the worst culprits for sitting on oneself. It is deeply not fun. You go to rest upon the usually comfortable seat, unaware that the spiteful bastard has surreptitiously cradled your jewels underneath you. Suddenly all is a deep and embarrassing pain, as you realise you only have yourself to blame for this agony.
I've never had much of an opinion of my balls one way or another. Except when I get hit in them, then I hate them. But that doesn't happen often these days.