Tech Deck Skateboarding (Handheld Games/Activision, 2001)
A skateboarding game where you play as what can be charitably described as a sentient potato and uncharitably described as a reproductive organ. It's extremely slow for a skateboarding game and a lot of the tricks happen automatically, which seems to defeat the entire purpose of the genre.
Test Drive 6 (Xantera/Infogrames, 1999)
I was looking forward to this one because I played a lot of Test Drive Unlimited 2 on PC and wanted to see how they adapted this series to GBC. The answer is "very badly." Even at 128 MPH you feel like you're barely moving and the engine noises are without a doubt the worst I've heard on GBC yet. It controls well enough, but everything else is a disaster.
Test Drive 2001 (Xantera/Infogrames, 2000)
The graphics and engine noises are much improved, but it feels like you're driving on ice and they've somehow managed to make both the place indicator and the turn indicator frequently wrong. I don't know how you release a racing game that doesn't always know what place you're in, but apparently they decided that was okay.
Test Drive Cycles (Xantera/Infogrames, 2000)
Although not quite as bad as the first Test Drive's engine noises, the ones in this game do a good impression of a dial-up modem that's stuck on one of the low notes. Hazards and other vehicles just pop up out of the void without anywhere near enough time to dodge, and it takes forever to get moving again after you've hit something.
Test Drive Le Mans (Velez & Dubail/Infogrames, 2000)
It has good music and graphics, but all the same control and visibility problems as the other GBC Outrun-esque games. It throws in some new ones on top of that by having really flickery pop-in and a weird bug that makes it look like the other cars are flying. It really needed a map instead of a tire indicator with how short the draw distance is.
Test Drive Off-Road 3 (Xantera/Infogrames, 1999)
If this looks a lot like the first game, it's because they came out two weeks apart and are both reskins of an NES game. Off-Road removes the map and has some extra track hazards, but inherits all of the sound and sense of speed issues.
Tetris DX (Nintendo, 1998)
It's Tetris. It doesn't have korebeiniki. I don't know what else to say about it.
Thomas the Tank Engine: Sodor-tou no Nakamatachi (Tamsoft, 2001)
This should have been back in the K's (for Kikansha Thomas), but Wikipedia inexplicably lists the English translation of the title in their list of GBC games despite the fact it only released in Japan. No one was deprived of anything by waiting this long to see it, though, because it's an extremely boring game about driving around slowly and replacing bits of missing track.