Famitracker is a music tracker program I use to create sound effects for Mega Man Maker and other shenanigans. It's designed to replicate NES hardware as closely as possible, so it's by far the best tool to achieve that authentic 8-bit sound. If you want to check it out yourself, I highly recommend these resources:

• Famitracker Effect Cheat Sheet
• How to Use Famitracker tutorial series by Ben Burnes
• Famitracker Effects Teutorial series by Teuthida