The Judge from the Ace Attorney games falls into this trope many, many times. From case 5 of the first game, this is his response to being told that a witness was using another character as his "puppet"...
Oh you mean someone who uses someone else, nevermind.
Masayuki occasionally in A Profile, though it's not always played for laughs. But one that is goes like this:
Masayuki: So, you have multiple personalities, huh? Awesome, I can have a threesome this summer!
Shirou in Fate/stay night has this problem when any of the Deus Sex Machina problems come up, as well as at the end of UBW good ending. To be fair, it really iskind of a stretch to link "not enough mana" to "have sex with Saber/Tohsaka". In their defense, there is actually an Oriental belief that while masturbation results in you 'releasing' energy, sex involves exchanging energy so either you lose nothing or gain something if your partner has more energy than you due to something about balancing energies. Incidentally, there are a number of martial arts schools that say you shouldn't wank before training but it's ok to have sex.