Walking in to the opposite sex toilet whether you noticed or not and ending up with looks that will scar you for life.
Someone walks in on you (especially in a number 2 situation).
Walking in on someone who threw up when you really need to use the toilet.
Conversations while peeing in the urinal – fear of exposure + homophobia + awkwardness all in one!
Waiting for people to leave the bathroom so you can come out of the stall after a noisy incident.
When someone decides to use the bathroom at a sleepover with the door open.
Being in the bathroom with your boss.
Drunken conversations waiting in line for the bathroom are ALWAYS awkward.