Pretty much anything thats not a standard controller for your console of choice.  So things like rockband gear, wheels, frag FX / turbo controllers cameras ect.

2 just the eye and a headset

Well overall its an extensive list.

SNES - you have things like the super gameboy and multitap
Gen - Sega CD though really an add-on than accessory
PS2 - racing wheel
PC - console controller converter
Wii - Wii Speak, perfect shot, 2 classic controllers (soon to be 3 with only 2 Wii remotes lol), Balance Board, Guitar, drums, looking into the 1080p upscaler next
360 - headset
PS3 - PS eye, MGS headset
Xbox - Pump it up pad
GC - DDR pad
N64 - Hey you pikachu mic
NES - lightgun
GB - link cables out the wazoo, magnifiers, external lights
GBA - recharge kit
DS - Sword stylus/keychain, Max Media Dock
PSP - Batman (the Joker) skin, improved thumb stick

So really the only console I didn't own accessories on would be the PS1... amazing unless gameshark counts then I had one for just about every console since the GB.

Does a final fantasy action figure count :P

Depends what you count as an accessory.

I would guess nunchuck is not an accessory as it is used in so many games.... but what about the Wii remote jackets (they were free though)

I have:
1 motion+
2 wheel plastic case things (one from MKWii one from F12009)

That's it really

I used to have the RAM expansion pak for N64, required for some games but I guess it is an accessory.

If you count other bluetooth accessories such as a keyboard for my PS3 then 8 :P
Keyboard, Bluetooth headset, 360 headset, Guitar hero guitar x2, rockband guitar, drums and mic

Current gen:

1x Guitar

1x FragFX V2

3x secondary controllers for 360/PS3 (2x 360 / 1x PS3)

1x wireless PC receiver (for the 360 controllers)

2x play and charge kit

1x headset (although that came with the 360 for free)

1x Wiimote+Nunchuck (I list it because I don't even own a Wii)

1x 360 faceplate + 1x console skinz + 1x controller skinz

1x PS3 trigger

more than I thought......

PC: USB Dualshock 1/2 adapter (to use Dualshock 1/2 controllers on a PC)

Xbox 360:
Two headsets
Chatpad (attached to my Gamepad)
Quick Charge Kit w/ 1 battery
256 MB Memory Unit (to backup game saves. Now that we can use USB, this thing is obsolete)
HORII Arcade Stick
Mad Catz SFIV Fight Pad
Four Sceneit? Controllers
Xbox Live Vision Cam (lol. It was a bundle pack-in)

Wii:
Classic Controller Pro (had it pre-ordered. Have to wait for it to ship)
Wii Motion Plus (ordered it with CC Pro. So I gotta wait for it)

Nintendo DS:
Flash Card kit complete with a GBA flash cart and a Rumble pack (lulz)
Some third-party stylus I never use

PS2:
DVD Remote Control
Boot discs and sensor blocking keys (to run unsigned code)
Sony 8MB Memory Card with custom firmware installed that allows me to run unsigned code without having to use the above mentioned boot disc and sensor blocking keys (more lulz)

PS1 (Laser is R.I.P. Doesn't work):
Internal Modchip
Three Memory Cards (I have a 120 block third-party card and another 15 block third-party card. I can't find my official Sony one)

Sega Genesis: I don't believe I have any special accessories for it. Just gamepads.

NES:
Game Genie (I still have mine and it still works)
Track Pad (for Track & Field)
Light Gun (for Duck Hunt)

250 GB WD 7200 RPM for my 60 gig, I guess that counts
G25
Frag FX
RB1 premium kit
RB2 premium kit
ion drum rocker
Beatles Guitar
Wireless mic
Playstation Eye
Jabbra BT headset
buzz quiz controllers
BT logitech KB+mouse

I had all kinds of things for my PS1, gameshark pro memory cards ect but thats all loooooong gone.

PC - G25 set (wheel, pedals and shifter), 1 Logitech Dual Action gamepad, 1 Rumblepad II gamepad, G11 gaming keyboard.

Wii - 2 Classic Controllers, Perfect Shot, Wii Zapper, 3 Motion +, wiimote charger, 2 wheels (one from MKWii other from... Monster 4x4 ), Balance Board, Wii Speak.

Damn, that's a lot. O_O