Do you mean official Sega stuff? If that's the case, then this is what I have.
a steering wheel, a flight stick, 2 arcade sticks, a 6-player adapter, a twin stick, a mouse, a backup ram cart, a stunner gun, a box full of varies gamepads, 2 s-video cables, 1 model 1 unit, 2 model 2 units (both are modded).
As far as third party... I have a 4in1 PAR, an Action Replay +, 2 Panther 7 lightguns, a SCART cable, and a few of those gamepads in the box.
I am sure there are a lot more goodies out there, but this is just what I have.