A student who is feeling desperate on a deadline is likely to turn to any method that may help them get that good grade. Sometimes, this involves cheating - hiring another student to do their work, buying performance-enhancing drugs to pull an all-nighter, or even lying about life circumstances in order to extend a deadline.
Other times, students may attempt to hit on or bribe a teacher into giving them a higher grade. Since this is obviously unethical on multiple levels (power dynamics, legality depending on ages, and integrity as an educator), it's up to the teacher to set a firm boundary and let a student know these offers aren't an option.
No, but I did have a student say that if I didn't improve her grade she'd tell someone I'd made a pass at her and the bad grade was retaliation for rejecting it.
I had to remind her that: