Cheat Engine

You'll find information about Cheat Engine here

like:
 * Memory Scanning
 * Debugging
 * Auto Assembler
 * Lua
 * Cheat Tables
 * Data Dissector (Structure definer/compare)
 * Speedhack
 * Plugin System
 * Cheat Engine Internals
 * DBVM
 * Building Cheat Engine
 * Help file (from the program)

Website: www.cheatengine.org