Japanese DS Game Substantially Different Than US?
Eurogamer has the story that the Nintendo DS title Mr. Driller may have a very different feature set in the US and Japan. From the article: "According to widespread reports - which we've been unable to confirm as we haven't got a copy of either version - the Japanese version allows players to engage in various multiplayer battles in groups of up to four players using just one of the DS's game cards, whereas the US version requires multiple copies to achieve the same result." Interesting, if cynical, decision.
The games don't have region codes, so provided you can locate an import copy and don't mind reading Japanese, you can do this as well.
Monstar L
There have been a couple times where US and Europe get a superior game while Japan gets shafted with an inferior version. See Maniac Mansion and Battletoads.
The Japanese version of battletoads had the difficulty level toned down by a large factor, while the US version of Maniac Mansion was a superior rewrite.
Actually, while I was on vacation in Tokyo I picked up Mr. Driller Ace for the GBA (GBA has no territory lock. Yay!) and it allows you to download the game to connected GBAs as well. Several GBA games do this.