Neat avatar, Skeet!
Essentially there are (I think) five 15,000 RPM hard drives, and four of them on the market at present. All are SCSI (of course) and in consequence expensive.
Seagate Cheetah X15. 9GB and 18GB. The first 15,000 RPM drive and for a long time the only one. Still a serious performer. Surprisingly quiet for what it is, but certainly not in the same league as a more modest-spin unit. I own two of these (well, OK, Tannin owns them, but I get to use them too) and I love them. They are generally regarded as amongst the most reliable drives money can buy.
Seagate Cheetah X15 36LP. 18GB and 36GB. Seagate's second 15,000 RPM drive replaced the original X15 about 18 months or so ago. Incredibly, it was even faster than the original. Several Storage Forum members have owned one, if I recall correctly. (I wanted one, but Tannin wouldn't let me spend the money.) Again, I've never heard the slightest whisper about reliability problems. They are very well-regarded.
IBM Ultrastar Z15. 18GB and 36GB. IBM's first, and so far only, 15,000 got horrible reviews. Apparently, it is very hot, very loud, ridiculously expensive, and not particularly fast anyway. I would be reluctant to trust one too much, though I daresay it's at least as good as a typical IDE drive. (SCSI drives are almost always more reliable than IDE ones, for the same reasons that Mecerded-Benz cars tend to be more reliable than Yugos. (On the other hand, a man who once owned two 45GB Deathstar 75GXPs in RAID 0 clearly leads a charmed life and could survive anything.)
Seagate Cheetah X15 Mark III. Not sure of sizes, too lazy to go visit Seagate to find out. The latest Seagate 15,000 should be just sneaking onto the market about now. It was announced about three or four months back. Not greatly faster than the outgoing 36LP, but I gather that it is quite a lot cheaper and much quieter. If I were in the market for another 15K, this is the one I'd buy.
Maxtor Atlas 15K. Maxtor bought Quantum a little while ago, so think of this as the first Quantum 15,000 if you like. I don't think you can buy them just yet, but I should imagine that when they arrive they will be an excellent unit.
Ahh ... is there a Fujitsu 15K? Or a Hitachi? Ain't it funny how quickly you lose touch with the market when you are not thinking about buying one just yet?