My favourite is 83 year old Leo Burt being in the list of most wanted to this day. Dude did an anti-war stunt in 1970, accidentally killed one completely unrelated physicist (and also millions of dollars in damages). Now his possibly buried corpse is still listed as "armed and dangerous" in the FBI "Most Wanted" page.

Second favourite was Dr. Rafiq Sabir still being in jail to this day after getting entrapped by Ali Soufan (yet another "I could've stopped 9/11 if not for those laws guys!" FBI Agent turned independent contractor), who asked him to treat fictional Iraq war combatants from a fictional branch of Al-Qaeda. You can actually go check his name in the US ~~Prisonhub~~ inmate locator.