SSBM has a couple other features and modes that can't be categorized with the rest, such as the gallery and name entry. Let's have a look, eh?
Gallery
As you progress through SSBM, you'll be earning coins. Play the single player game or battle it out in multiplayer modes, and your coin total will increase. When you feel you're ready, you can take them all the the bank and cash out for some character trophies. The more coins you put in, the higher the chance that you'll get a rarer figure.
SSBM has trophies of almost every Nintendo character ever created. The gallery mode allows you to look at the trophies in 3D, and read up on their history. Much like the character bios section in the original SSB. There probably isn't any practical reason to collect them, other than wanting to see just how many of them are jammed into the game. Current estimates put that number at in excess of 192, so you'll be busy for quite a while.
Name Entry
It's a simple concept, but a welcome one. Now instead of wallowing in anonymity, you can get credit for all of your high scores and accomplishments in SSBM. Once you enter a name, you can save all of your battle statistics and keep a record of everything you've done. Finally, we might just get a statistics screen that's actually meaningful.
And for the record, SSBM requires 11 blocks of memory in order to save. Just a heads-up to anyone with a memory card that's almost full.