1. Corduroy. (Honestly, there's nothing that's sexy that isn't sexier if both guys are wearing cords)
2. Sex in theatres.
3.Kissing. I know EVERYBODY has it, but that just proves how good it is.
4. Blowjobs and fingerfucking. Particularlly if it's the 'receptive' partner's first time...
5. Angry/Hate sex. When one or the other is VERY angry, or when lust overcomes mutual loathing.
And nothing against het/femmeslash, but it just doesn't float my boat.
(Also, I know fandoms are at the autor's descresion, but my favorite pairing (Mark/Lucas), is crimanally underrepresented.)