Harrison Barnes is probably the most memorable. At the time, it hurt like hell....but things turned out ok. Really, until UNC made the Final Four in 2016, the last bad thing to happen for us against UNC was the Barnes pick.
One that really stung at the time for those following recruiting back then, was the recruitment of Jon Brockman. When he shunned us for Washington it was a tough day. I thought he had Duke written all over him. He would have started four years at Duke and really changed the dynamic of those teams.
Others....
Patrick Patterson - just because we needed a big man in the worst way at the time
Greg Monroe - we were the perceived leader, he visits Georgetown and commits before he leaves
Brandan Wright - UK and Duke were widely considered the favorites, when he picked UNC after his visit there it even shocked them....I remember Lawson saying he never saw a guy less excited than Wright on a visit
Shaun Livingston - Losing Shaun to the draft and watching Luol leave after a year was like getting kicked in the nuts with steel toe boots....our 2005 team, despite losing those two, was still a 1-seed in the NCAAT....but we probably overachieved