"Meh." (Alternative: sing "Is That All There Is?")
"You know, I think I may be gay." (Replace with "straight" if your partner is same-sex.)
"Well, everything seems to be working. If that part gives you any more trouble, just bring it down to the shop."
"I'm rolling double twenties!" (Unless your partner is an RPG geek, in which case s/he'd probably find it funny.)
"You validate parking, right?"
Any religious chant, particularly if done in synch with the act. Especially recommended: "Mea culpa, mea culpa, mea maxima culpa..." (while beating your chest with one hand); "Yitgadal veyitkadash shemei rabba..."
"At last, we have opened the portal. Enter, O Dark One!"