My fantasies change over time - I can't even really say that I have specific fantasies. It's more like I've been preoccupied by different (general) themes at different periods of my life. Right now I seem to be excited by dreams of exposure and humiliation.
My (currently) most common lewd fantasy involves being used as an experimental/erotic model by a dominant female friend. She takes pleasure in tasking me to do increasingly daring and humiliating postures and scenes. The photographs she naturally shows to friends...
My most surprising lewd fantasy (in the sense that my friends wouldn't expect it) is to be sexually used by an older, perhaps overweight man. (This fantasy has the added weirdness that in my fantasy the "older man" is probably much younger than I am in reality... Age dysmorphia?)
My (perhaps) most embarrassing lewd fantasy is to be sexually (ab)used by young men - twinks - so cute that their mere existence humiliates me, and makes me want to abase myself before them, to worship them. I'm not primarily thinking of a gang-bang scene, but rather a long-term arrangement were the twinks use me as a shared property to be used as needed.