Did you know that different characters hang at different heights from ledges? This actually matters since a bunch of moves can only hit some characters off the ledge. If two characters are on the same "level", it doesn't necessarily mean they are equal; I just couldn't find a move that could only hit one and not the other. If you can find a move that breaks up that massive block of 12 characters, that would be pretty awesome (I spent something around an hour and a half and couldn't find anything that worked).
Oh, and you do notice that characters bob up and down on ledges. This only considers the highest point of the animation. That's why Ness and Lucas rank so poorly; they are practically on top of the stage during a particular part of their ledge dangling animation.
Samus's fully charged Charge Shot can hit off ledge:
Donkey Kong, Olimar, Charizard, Ness, Lucas
Samus's fully charged Charge Shot can't hit off ledge:
Yoshi, Meta Knight, Pikachu
Captain Falcon's down smash can't hit off ledge (optimum range):
Mario, Bowser, Jigglypuff
Toon Link's down smash doesn't hit off ledge (roll into ledge):
Luigi, Ice Climbers, Squirtle, Ivysaur
King Dedede's down smash doesn't hit off ledge (roll into ledge):
King Dedede, Mr. Game & Watch
R.O.B.'s down smash can't hit at close range (roll into ledge):
Toon Link
Meta Knight's rapid jab can't hit at close range (roll into ledge) / Sonic's down smash can't hit at close range (roll into ledge):
Wario, R.O.B., Kirby
Ice Climbers down smash can't hit at close range (roll into ledge):
Link
Samus's down smash can't hit at close range (roll into ledge):
Sheik
Ike's down smash can't hit at close range (roll into ledge):
Zelda, Ganondorf
Zelda's down smash can't hit (roll into ledge):
Peach, Zero Suit Samus, Pit, Fox, Falco, Wolf, Captain Falcon, Lucario, Marth, Ike, Snake, Sonic
R.O.B.'s down smash can't hit at all (optimum range) / Diddy Kong's down smash can't hit (roll into ledge):
Samus
Jigglypuff's grounded Pound can't hit:
Diddy Kong
For a quick application, when looking for which of your moves can hit ledges, try them against Diddy Kong. If they work on him, they work on everyone.
Oh, and you do notice that characters bob up and down on ledges. This only considers the highest point of the animation. That's why Ness and Lucas rank so poorly; they are practically on top of the stage during a particular part of their ledge dangling animation.
Samus's fully charged Charge Shot can hit off ledge:
Donkey Kong, Olimar, Charizard, Ness, Lucas
Samus's fully charged Charge Shot can't hit off ledge:
Yoshi, Meta Knight, Pikachu
Captain Falcon's down smash can't hit off ledge (optimum range):
Mario, Bowser, Jigglypuff
Toon Link's down smash doesn't hit off ledge (roll into ledge):
Luigi, Ice Climbers, Squirtle, Ivysaur
King Dedede's down smash doesn't hit off ledge (roll into ledge):
King Dedede, Mr. Game & Watch
R.O.B.'s down smash can't hit at close range (roll into ledge):
Toon Link
Meta Knight's rapid jab can't hit at close range (roll into ledge) / Sonic's down smash can't hit at close range (roll into ledge):
Wario, R.O.B., Kirby
Ice Climbers down smash can't hit at close range (roll into ledge):
Link
Samus's down smash can't hit at close range (roll into ledge):
Sheik
Ike's down smash can't hit at close range (roll into ledge):
Zelda, Ganondorf
Zelda's down smash can't hit (roll into ledge):
Peach, Zero Suit Samus, Pit, Fox, Falco, Wolf, Captain Falcon, Lucario, Marth, Ike, Snake, Sonic
R.O.B.'s down smash can't hit at all (optimum range) / Diddy Kong's down smash can't hit (roll into ledge):
Samus
Jigglypuff's grounded Pound can't hit:
Diddy Kong
For a quick application, when looking for which of your moves can hit ledges, try them against Diddy Kong. If they work on him, they work on everyone.