I'll go first (duh)
One time, I was sitting on the toilet doing the doo doo and a spider came from the ceiling right in front of me, I wasn't even done and I didn't have anything to kill it with so I grabbed a stepping stool and smashed it into the ground and killed it.
Now it's your turn.
Edit: Baby Spiders hatched Inside my ceiling fan and invaded my room, needless to say I slept on the couch that day.
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Not as bad as some of these, but once I had to go to the bathroom in the middle of the night and as I'm leaving my room a cockroach scurries up my leg. [spoiler]I'm proud of myself for not waking up my family.[/spoiler]