Console Information

Sega's answer to Nintendo's Game Boy.

Like the DS/3DS, recording gameplay footage of the Sega Game Gear requires modification.

There is at least one service you can find online that accepts AV mods

http://www.otakus-store.net/en/game-gear-master-system/44-game-gear-tv-mod.html

and even occasionally a 'Buy it now' option on Ebay

http://www.ebay.co.uk/itm/Console-Sega-Game-Gear-Sortie-TV-Port-MD-Alimentation-Cable-video-/151070816151?pt=FR_Jeux_Vid%C3%A9o_Consoles&hash=item232c85b797

List of Game Gear games playable on other consoles

Most of the games on the Game Gear are very likely to have a Master System version, however not every version is 100% the same.
Fortunately these GG versions are available via various Collections Re-releases: As of 26th June 2013

Director's Cut version of Sonic Adventure

All 12 Game Gear games are available to play on either the Gamecube or retail PC version of Sonic Adventure DX: Director's Cut

'*'Also available on the PS2/Xbox version of Sonic Mega Collection PLUS

Sonic the Hedgehog *
Sonic Chaos *
Sonic Drift *
Dr. Robotnik's Mean Bean Machine *
Sonic Labyrinth *
Sonic Blast *


'**' Also available on the PS2/GC version of Sonic Gems Collection

Sonic the Hedgehog 2 **
Sonic the Hedgehog: Triple Trouble **
Sonic Drift 2 **
Sonic the Hedgehog Spinball **
Tails' Skypatrol **
Tails Adventure **

3DS Virtual Console

There's more people having a modified 3DS than people having a modified Game Gear system, so this list is pretty useful.
The only disadvantage is that Imports of portable games hasn't been released on eShop and 3rd party/licensed games are even less likely to appear.

Dragon Crystal
Shinobi (aka The GG Shinobi)
Sonic the Hedgehog: Triple Trouble
Sonic Labyrinth
Sonic Blast
Columns
Dr. Robotnik's Mean Bean Machine
Shining Force: The Sword of Hajya
Sonic the Hedgehog
Defenders of Oasis
Tails Adventure
Crystal Warriors
Sonic the Hedgehog 2
G-LOC: Air Battle
Master of Darkness
Sonic Drift 2