One day, I was on the metro and it was quite busy, although not completely crowded. This random guy kept moving as close to me as he could, his crotch against me, even though there was ample room to avoid doing so, and he took advantage of the accelerations and turns to touch me. I tried to move away but he kept coming back.

Then I just stepped on his toes as hard as I could (and I can!) and said a loud “I’m sorry” in the most insincere tone.

He immediately stopped bothering me and didn’t try again. And boy how good that felt!