Here's ollection of glitches, at least one of which is potentially game-breaking:
Minor/Cosmetic:
-When wearing the Kimono, Red will frequently get discolored
-There's a rock in the first level of Victory road that the game treats as a cliff, meaning you can jump over it
-The screen placement of Pokemon when using a healing item isn't remotely consistent
-The item doesn't always appear on-screen while in the screen showing the item being used
-Sometimes there seems to be a character limit of 15 on the text displayed after such a healing item is used. After this limit, the game will display a period. For example, if this happens when using a Super Potion, the game will display (period included) "Super Potion wa."
-At least sometimes when Red completes the Date-Finding competition, he doesn't get the promised Master Ball.
Major/Gamebreaking:
-Changing costumes while surfing, at least while in the Safari Zone, may return the Pokemon being surfed to its ball, putting Red in a walking state. While in this state, Red cannot get back on land by any means, with the exception of perhaps teaching Surf to a Pokemon, though I have not tried that. If this happens and you save, you might be screwed and have to start the entire game over.