This idea started over in T3hPwnisher's log. It seems like it would be pretty entertaining to hear what people have done. I'll start off with a few things:
-In 5th grade I thought I was the shit for doing dumbbell curls for sets of 200 with around 5 lbs. It looked like I had golf balls for biceps and I thought it was cool.
-I missed a deadlift PR in training after multiple attempts. I remembered how I read about another guy missing a PR and hitting it the next day. I thought there's no fucking way I'm going to miss it tomorrow. I went into the gym only for the PR and couldn't even get the last warm-up attempt to budge.
-The most obvious one: working up to over 225 for quarter squats to show the guy next to me that I could squat more than him.