Ok, here is what I have off the top of my head. Some items were released here too, but I'll list them all.

Saturn & DC Twin Sticks
Saturn Densha de Go! controller
DC fishing controller(s)
DC arcade stick w/ the green buttons
DC gun(s)
Saturn gun(s)
Saturn arcade stick
US & JPN maracas
DC JPN Steering wheel
Pop n' Music controller
Mission Stick
DC DDR pad(s)
PS2 Drum mania w/ game set
PS Beat mania controller
PS Guncon(s)
PS2 Guncon(s)
PS Jet de Go! controller
PS "The grip" controller
PS2 Para Para Paradise set

I just got a new one for the PS2. It's like the Densha de Go! controller but for trolleys. It's pretty! :P

Soon to have the Trance vibrator and the Tam Tam controller and game. Also looking into the PS2 drum game with the Tat Ta con?, I think that's it's name.