I blush like crazy when I'm tickled, I feel super embarrassed when my psychological walls crumble and I squeal and squeak and giggle and I think to myself, "I didn't know I could even make sounds like that?!". I'm super sensitive to teasing and humiliation though, so if someone makes fun of me I get sour and don't want to be touched anymore.
It's like your body is exposing it's vulnerabilities to your play partner, and if it's received right then the situation turns red hot, but if not everything goes ice cold.