Bonk (in the sexual sense of the word) - it just sounds so corny and immature.
Va-jay-jay - ugh! What is it with grown-ups who can't use grown-up names for their body parts? Like 'bonk', it just sounds so corny and immature.
I must admit I recently used 'va-jay-jay' in one of my posts, but only because it rhymes with 'all the way'.