Wipeout got an entry on the N64. You could have guessed that from the title. It's pretty much Wipeout XL / 2097 but not quite. More importantly it's the third anti-gravity racing game Rob remembers playing.
Bit of a corrections column needed for this one: Sony wasn't stopping Psygnosis from doing what they wanted to do at this point in time. That all stopped with Wipeout 3 though. Wipeout 64 was indeed Psygnosis developed and not by a mysterious extra party. The tracks are modified, mirrored versions of tracks from the previous Wipeout games with new skins. It's hard to tell though.