What are some of your favorite videogame accessories or peripherals?

Controllers also count, but we have had many topics talking about favorite controllers so I invite you to think about other types of accessories.

One accessory that I have really enjoyed recently is the PS5 Pulse 3D wireless headset. I use it for gaming on my PS5 and PS4 and I've really noticed the 3D audio difference. I also use it to watch movies and TVs so I don't disturb other people in the house. Also I am glad they included a simple aux cable so I can use it as a wired headset. I use it with my laptop.

What about you?

The Game Boy Player! I didn't have a GBA yet when I initially got this peripheral but being able to play Pokémon Gold/Silver on my TV blew my mind!!! And when I finally was able to get a GBA, those games on my TV blew my mind even more

Does unnoficcial stuff count? 

If it does, this marvel from Aliexpress that allows you to dump your GB/GBC/GBA cartridges and copy your save files and inject them. Thanks to this, my original Pokémon Blue and Silver save files with a complete Pokédex will not be lost:

If we are talking legit stuff... I'm gonna say the Link Cable for both GB/C and GBA. I know, I'm a Game Boy sucker xD

ASCII Flight Stick Dreamcast.

While I love the DC VMU I actually like the Sony PocketStation more because of the design.

SEGA Dreameye. Worlds first console camera. It came with Software called Visual Park. The camera could also be used as a digital camera by taking it off the base. It had a video sharing service. Email and can call people.

The Mega Drive XE-1 AP. The worlds first Dual Analog Controller and had shoulder buttons...in 1989.

NES Advantage was cool, and the six-button Genesis controller is a must-have for some games (SF2, MK3). The little coiled light attachments we use to use on our Gameboys were a necessary evil as well. Oh, and there were some cool dance mats back the day. It was always a fun challenge to try beating games using them. lol

The Wavebird controller and the Game Boy Player for the Gamecube. Before that, the Super Game Boy for the SNES.

Does the Switch dock count?

The Guitar Hero guitar controller was great. Such fun games back in the day.

The GameCube Controller adapter that is compatible with Wii U and Switch
I know it relates to controllers, but it's not a controller itself.

VR headsets

Playing Lionheads black and white with the Essential Reality P5 Glove.
You are literally the hand of God in the God sim.

Motion controls years before the Wii.