"3 Little Birds" is my favorite Marley song (and it might be one of the best songs of all time - definitely makes the first cut) ... so of the ones unmentioned, I'll dig a little further back into the early Marley era for some favorites.
Sometimes we forget that Bob Marley and the Wailers weren't just the seminal reggae band - they also pioneered dub and ska, putting out some of the best mid-tempo stuff of the time:
"Guava Jelly/This Train" - this version is a beating, a near-rival for "3 Little Birds"
http://youtu.be/1Cw_8ko6PrI
"Mr. Brown" - the best song about Jamaican ghosts, period:
http://youtu.be/3VbwibwTZrM
"One Cup of Coffee" - first single from a 17yo Marley ... the voice isn't developed, but creates a pantheon-level first-wave ska track anyway:
http://youtu.be/he5Dv0tSr3Y
"Simmer Down" - Collaboration with the legendary Skatalites, showing the amazing amount of talent working in a relatively small population ...
http://youtu.be/ItIkqcss0iU