Mario Party Advance does a lot with a little. There are eight 2-player competitive mini games through the Single-Pak link mode. Then, all 50 games can be gifted to linked GBAs and they can be played on that stand-by GBA until the power is turned off.
Like the mini-games, Gaddgets (named after Prof. E. Gadd originally starring in Luigi’s Mansion) are micro apps that can also be send to empty GBA users. Most of these apps are silly and have no point but there is no denying their creativity. Mario Party Advance also has some great spritework and an underappreciated sound track.
And don’t forget about Mario Party-e which was a board game that also used the GBA e-Reader (also really fun and creative).