Master System Joypad
The MegaDrive is backward compatible with the Master System joypad.
It has a D-PAD and 2 buttons.
3 Buttons Joypad
The standard MegaDrive control pad.
It has 3 buttons (A,B and C) and a START one.
6 Buttons Joypad
The 6 MegaDrive control pad was mainly out for Super Street Fighter (with the 3 Buttons one you had to switch between kicks and punch by pressing start).
It has 3 new buttons (X,Y and Z) and a MODE one.
By pressing the MODE buttons while powering on the console the joypad will behave like the standard 3 Buttons one (some games didn't handle well with the 6 buttons one).
Arcade Power Stick
The first version of the Arcade Power Stick, it has 3 buttons along with a Megafire switch for each one (it's simply an autofire) but the speed of the autofire is the same for each buttons (it only have one speed control slider).
Arcade Power Stick II
The 6 buttons version of the Arcade Power Stick.
It adds two speed for each buttons and a 3/6 buttons switch mode.
Sega TAP/Multiplayer/Team Player
The multitap for the MegaDrive.
There is two version, the first one plugs only on the first control port while the second plugs on both port (and is compatible with the EA-4WAY adapter)
The Japanese/European version of the mouse.
It have 2 buttons (A and B), the C buttons is on the ball itself and has no START button.
It's not compatible with the Mega Mouse.
The US version of the mouse.
It have all the 3 buttons and the START one.
It's not compatible with the Sega Mouse.
The Menacer is a infrared gun for the MegaDrive.