Here is a list. (I will admit I am guilty of a few of these.)
2. Sex is never messy.
3. No one gets knocked up unless the plot demands it, even if condoms are never mentioned.
4. Virgins always orgasm their first time out.
5. Every woman orgasms from penetration alone.
6. Even if she hates her rapist he's still going to make her climax.
7. The average penis size is 9 in.
8. Every BDSM practitioner has a full dungeon in their home.
9. Lube is never necessarily.
I know there's more--what have you got?