Sex While She's on Her Period
Scenario: This can go one of two ways. Either she's the one who's totally game to get down to business despite the potential mess and you're squeamish; or, you're game, and she has hang-ups about it.
Solution: Ultimately, this one comes down to personal preference, so you shouldn't feel ashamed of being on either side of the fence. That said, a generous partner will try anything once. Give it a shot, and if it's still not your thing (or hers), at least you tried.