These are the mappers that I have Reverse Engineered.
Mario 7 in 1 - Mapper info.
Nintendo World Cup / Super Spike - Mapper info.
The Rumble/Game Station - Handheld NES + Multi mapper info.
Super HiK 7 in 1 - Weird MMC3-based multicart.
Super HiK 4 in 1 - Another weird MMC3-based multicart.
11 in 1 Ball Games -The worst multicart design.
Super 1000000 in 1 - An even weirder MMC3-based multicart
Caltron 6-in-1 Info - info on how the mapper works.
Pirate SMB2j Mapper info - The cart version of this famous game.
Another Pirate SMB2j! - Totally different design from the first one.
Mario Baby Mapper info - Cart version of Konami's FDS game Bio Miracle.
Golden Game 150 in 1 mapper info - A cool 150 in 1 multicart.