The list is long:
1) Anything outdoors. Gravel, dirt, grass, bugs, boiling sunshine, concrete, awkward lawn furniture, and the like are all huge turnoffs.
2) "Fuck, fuck, fuck! Oh, fuck! Fuck, fuck, fuck! Fuck! FUCK!" Inarticulate or illiterate, not sexy.
3) Missing hair, especially pubes.
4) Preening
5) Abuse or disrespect. Spitting on the other man.
6) Rape
7) Incest
8) Tearing clothes off of self or others when the plot is that the men are not at home and have no other clothes. Complete unreal.
9) Paddy O'Brian's accent. Never, ever, leave the volume on.
10) A top who behaves like the bottom is not important, or worse, like the bottom isn't suffering enough
11) Pretense of cuckolding
12) Pretense of public sex
13) Pretense of clergy sex with a confessing penitent
14) An aggressive bottom when the top was already doing just fine. The aggressive bottom often stops the top when it becomes obvious two cannot drive
15) Dirty bodies
16) Heat and sweat
17) Grunts by foreign men who are producing porn but for the Western (English) market. It seems to demean them.
18) Pretense of kicking the bottom out when the sex is over. Not funny.
19) Women
20) Changing sex positions according to script. Both men suddenly jump to where they are supposed to be at the forth position.