Personally, I usually choose Seagate and Western Digital.
A lot is personal preference, though. It's kind of like asking which car make you should buy. It quickly deteriorates into horror stories about off models from each maker.
In recent days, for systems I've built for myself and others, I've used the following...
2x Maxtor DiamondMAX - 1 failed
2x IBM Deskstar - 2 failed
3x Seagate Barracuda - 0 failed
~10x Western Digital (Mostly Caviar, though occasional other models) - 1 failed (a Caviar)
take that for what it's worth.
