Jerry Auzmah. I competed against him in track in high school. He was insanely fast, built like a pro when he was in HS. His team, Saint Peter-Marian, was horrendous, he was the only person who placed in the top 3 in any event for SPM at the meet, winning the 100 (he had a bad start on my schools crappy dirt track, but by the end it wasn't even a close finish) and placing third in the long or triple jump. His explosion was just off the charts. As a scrawny freshman distance runner he looked like a full grown man to me. Everyone knew he was a big deal and he was super polite to everyone. After he went got drafted and started his career with the Bears (making the Pro Bowl as a returner) he set up a scholarship fund for low income kids to go to SPM, because his family were immigrants, he got a scholarship there and he credits SPM with giving him the opportunities that led to the NFL.
The other encounter I had with great, but not famous athletes was in at the MIAA Indoor track and field Championships at the Reggie Lewis Center in 1999, when Franklin Sanchez and Andy Powell ran 8:49 and 8:50 indoor 2 mile, destroying Alberto Salazaar's state record. Distance running is fairly boring for spectators, but those two absolutely flew down the track during that race. An 8:50 two mile requires you to average a 1:06-ish quarter mile. That is damn hard for most in shape people to do one time, outdoors. But 8x, indoors, is insane. I had never seen so many people screaming and excited about a 2 mile race in my life and I spent 10 years competing in and attending track meets at high levels. Those two were the best high school distance runners in the country for a couple of years, and it wasn't even close.
Sanchez set a few American Junior records ran at the World Cross country championships, finished 6th in NCAA XC championships as a freshman, went pro for a bit and then quit running. Powell spent most of his collegiate career injured, but was on several NCAA champion teams, then got into coaching.
Watching the London Olympics, Matt Centrowitz became the first American win gold in the 1500m and they're interviewing HIS coach, Andy Powell. It put things into perspective for 31 year old me, to know that a guy who as a high school kid who was so much better than me and almost everyone else, in in the country, was toast before he was 30 and the closest he came to Olympic glory was coaching someone else to gold. The strata of the top athletes is insane. You can be great in HS and not even make the team in college, you can be good in college and shit in the pros, you can be good in the pros, but not be great. These people are the .0001 % of top 1%.