DNF'd - I passed out once 6.5 miles into a 7 mile race. Woke up 45 minutes later in the emergency room with every muscle in my body cramping....not fun. I thought since I was a college runner I didn't need water in a race, bad mistake.
DQ'd - I got DQ'd in high school 1600m race for running on the line - the first 3 finishers in the race all got dq'd for the same reason, weired (I was second so I was just following the leader!).
DFL - I don't think I have, but my senior year of college I only beat 20 people at Nationals for D1 XC...I remember seeing a couple of guys drop out the last mile and getting so mad because it made me look that much worse.