It's a pretty small genre, even if you count the ones with wheels (boo!), but there are still quite a few of them. Due to the fact that pretty much everybody here is a fan of the Wipeout series, posters can only mention one Wipeout game each, and they each have to include at least one non-Wipeout game with it. Otherwise, this thread's going to get a bit repetitive.
I'll start with my top five:
1. Wipeout HD (PS3)
The pinnacle of hovercraft racing excellence! It's technically deep, it beautifully balances racing and combat, it has original and varied game modes, and its graphics, music, and general polish are almost unparalleled - it'll be a long time before something comes along that's better than this.
2. F-Zero GX (GameCube)
The other pinnacle of hovercraft racing excellence! It may not have the depth or subtlety of the Wipeout games, but it makes up for that with its intensity, speed, and truckloads of content, not to mention its crazy track designs. There's also a custom ship editor, a story mode, Captain Falcon - it's easily on par with Wipeout HD, and even better in some areas.
3. Hi-Octane (PC, PlayStation, Saturn)
It's one of the ugliest games ever created, and it was developed in less than two months. So how does it manage to be so fun? By combining ultra-floaty futuristic handling with wide, forgiving tracks, putting an obscene emphasis on combat and destruction, and carefully balancing the gameplay to ensure that everything works perfectly as a whole. Also, deathmatch mode.
4. Quantum Redshift (XBOX)
Designed by our own Nick Burcombe, of all people, Quantum Redshift brought futuristic combat racing to the XBOX for the first time. With incredible graphics (especially the raindrop effect), imaginative, arcade-style course designs, and an interesting - albeit sadly underdeveloped - rivalry system, it's a masterful example of the genre.
5. Galaxy 5000 (NES)
Surprised to see an NES game on this list? Don't be. This little isometric gem is really quite good, with fast-paced racing action married to a basic money and upgrade system. Exuding the same sort of accessible playability that characterizes series like Super Smash Brothers and Mario Kart, Galaxy 5000 is among the best that the NES has to offer.
/games
Well, I'm done rambling; now it's your turn.