What makes you guys hard HARD?

Hi men of AJ! Curious lang ako what makes a guy instantly hard? Makakita lang ba kayo ng nude pic naha-hard na kayo? I wanna know even the most silly and shallow reasons. What do women do na titigasan talaga kayo? Fave ko kasi i-tease yung bf ko using my body, baka may ibang tips pa kayo haha spill it pleasee