GC SET files - Object layouts from the GameCube version of SADX, with more background objects than the PC version.
Super Sonic hack - Loads Super Sonic instead of Sonic.
Alternate Character hack - Loads the alternate characters in 1P mode.
No Battle hack - Loads the original Dreamcast intro, title screen and menu backgrounds.
Dreamcast Models - Character models and textures from the Dreamcast version, converted for the PC port.
Character Select hack - Allows you to load the character of the opposite aligment by holding L, and the 2P alternate by holding R.
Sonic 2 Hacks
Not-so-Super Sonic 2 - A hack with stuff, including Amy Rose. Currently not being worked on.
S2Boost - A Sonic Rush style boost in Sonic 2.