And before you ask, no I am not kidding.
Some Pokémon, throughout the games, especially the early Gens, have had sprites where they were displaying a gesture that probably wasn't really supposed to be meant for kids, as far as I'm concerned.
Sandshrew, for example: 
Other than that, are there any others? I was genuinely curious, as these are an example of the very few times Nintendo slips up when censoring stuff, and I figured this would be a good exhibit for such a phenomenon for the world to see. ;-]