Here is the post from the Gamefaqs topic made by Shade.
shade_30
Posted 2/9/2008 9:53:27 AM
message detail Here is the list: (bit messy, gamefaqs doesn't seem to support space/tab)
Mario: Yes
Luigi: No
Peach: No
Koopa: No*
Donkey: No
Diddy: No**
Yoshi: No*
Wario: No*
Toon/Link: No
Zelda/Sheik: No
Ganondorf: No
Samus: No***
Zamus: No
Pit: No*
Ice Climbers: No
Robot: No*
Kirby: No
Meta Knight: No
Dedede: No*
Olimar: No*
Fox/Falco/Wolf: No*
C.Falcon: No
Pikachu: No*
P.Trainer: Yes
Lucario: No
Purin: No
Marth: Yes
Ike: No
Ness/Lucas: No*
Game&Watch: No*
Snake: No
Sonic: No*
Yes = blocks knockback
No = FS has normal effect
* = Can't block initial (if there is one), but can block parts of the FS as it works normaly.
** = Uncertain as I cannot test propertly, It's either No or No*
*** = Blocked Initial, but FS stays too long for it to be fully blocked
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Owner of Super Smash Brothers: Brawl
All Characters & Stages Unlocked :D