Mega Drive / Genesis
There’s a wealth of nice mods that can be performed on the Mega Drive / Genesis to enhance performance and unlock potential goodies that exist inside the Hardware. This is because the Master System utilised some use of dual-region and this was embedded into future consoles later on. Fortunately for us, these mods are inexpensive and easy to do (while still being pretty exciting for fanboys)
There were a few revisions of the Hardware for the Mega Drive and the obvious naming of Genesis in North America, there are some basic components under the hood. User, Ace of the Sega-16.com forum has an excellent run down of the differences here.