Sonic Tweaker

Sonic Tweaker is a utility by drx that edits various values for Sonic 1, Sonic 2, Sonic 3 & Knuckles and Knuckles' Chaotix. In addition to a checksum fixer, the program includes the following:

Demos Editor
Object Editor (which deals mostly with variables for in-game bosses and Sonic/Tails)
Palette Editor
Text Editor
Water Editor

DOWNLOAD
The current version (v.0.04) of Sonic Tweaker is available here (363KB).