There's a GeForce2 MX 400. It's the fastest GeForce2 MX.
Series went like this:
GeForce2 MX (original MX, not slowest)
GeForce2 MX100 (slowest)
GeForce2 MX200 (almost as slow)
GeForce2 MX400 (pretty quick)
GeForce4 MX420 (like GF2 MX200)
GeForce4 MX440 (not so bad really, think GF2 Pro)
GeForce4 MX460 <- (this one is actually pretty wicked lol. It flopped tho cuz it was too $$.)
Wikipedia actually has some decent model info (cuz I put most of it up, lol).
Then the next shopper-robber DX7 GF4 came out, the MX4000. Though it's not actually called a GF4. GeForce MX4000.
There may be other models out there, but these are the major ones that got significant press. GF4 MX was really made to compete with the likes of Radeon 7500, and to end the line of more expensive-to-build GeForce2 cards (GTS, Pro, Ti, Ultra). They were good at that, with MX440 ougunning the Ultra sometimes, but they lasted WAY too long. I can't believe people still buy them in the MX4000 variety. Yuck. You can get a nice Radeon 9700 PRO for less, lol.