I'm not sure of the worst, but a big one is people having expectations of me; forcing a sense of obligation onto me. For example:

• People expecting a present from me.
• People expecting me to do a favor for them.
• Women who expect me to do everything for them—to be at a woman's every beck and call—just because they're of the female gender.
• People who expect me to do something of a social nature, just because of some arbitrary social rule or tradition that I have a choice—like everyone—to do.

Probably others, but those come to mind.