Binding of Isaac: Rebirth Message Board  

Not many have been found yet, but here's the current list that I've seen of special seeds:

FART SNDS - Most sounds are replaced with fart sounds
CAM0 K1DD - Isaac is almost entirely invisible by making him colored like the floor
B00B T00B - Makes that game look as if it's being played on an arcade machine
BRWN SNKE - Isaac leaves a trail of poop as he walks
SL0W 4ME2 - Everything is slow motion when Isaac stands still, but speeds up when he walks.
BASE MENT - All floors are the basement. (endless loop, you can't advance)
BL1N DEYE - All enemies are invisible.
CHAM P10N - All eligible enemies spawn as their champion versions.
DRAW KCAB - Movement and firing controls are reversed.
KAPP A - Turns Isaac's sprite grey like the Twitch.TV Kappa emote.
HARD HARD - Full effect unknown, seems to be an alternative hard mode.

There are *supposedly* over 100 special seeds in rebirth. Here are what we do know about these seeds thus far:

These special seeds will either add a filter to the game, change the graphics, or sound effects. These special seeds won't generate the same rooms every time like a normal seed would. It only applies the effect. Special seeds will not contain I, O, U, or V.

Edit: Some new ones:

NRTH LION - Puts a heart in the seed section, just an easter egg.
P4GJ QFWH - All doors are curse doors.
SLOW 4MW2 - Music speed changes based on movement speed
AML6 29T4 - Unknown, but during a livestream from the devs, a "rare trapdoor" appeared that they wouldn't explain. Same may show up on that seed.


[Edited by Shimatsu, 11/5/2014 8:06:56 AM]

Edit 2: The "rare trapdoor" is probably the special item rooms, which are callouts to the original Legend of Zelda. You go down a ladder, fight an enemy, and get an item.

[Edited by Shimatsu, 11/5/2014 9:16:26 AM]

[Edited by Shimatsu, 11/6/2014 4:50:03 AM]