Inappropriate on public transportation

I cried on the L this morning.

It was a quiet, tears-streaming-down-face kind of crying, not a loud, sobbing, fist-pounding freak out, but crying nonetheless.

This made me start thinking about all the inappropriate things I've seen on public transportation. These include:
- woman plucking her eyebrows
- man clipping his fingernails onto the ground
- woman brushing her hair and then cleaning the brush out and throwing the hair on the floor
- countless examples of nose picking/eating
- loud and graphic conversations about sex
- the painting of fingernails (this was both ill-advised given the motion of the train AND smelly)

I'm curious what other inappropriate things you've seen on public transit, which many seem to perceive as a space so public that it might as well as private.

Anything to add?