Depends on what your needs are and how you define "best".
If price is an issue, I've gone with Western Digital MyBook's and haven't had many problems with them. I know others have been fans of LaCie and Seagate. Probably get a decent drive around $110-120
If you want something a little more durable, I also really like OWC Mercury Elite's. They use higher quality drives from Hitachi and support their products with longer warranties than the low cost guys. They also cost a bit more. Cheapest 1TB drive they have that supports FW800 is $180. They also have a FW400/USB2 only drive that goes for $150.
I know some people swear by G-Tech's drives, like the G-Drive Q, but I've heard they've been cutting back on the quality of components they're using (have nothing to base this on other than talking to some industry guys at Macworld, though. Used to use Hitachi but apparently not anymore). Similar in features and warranty to the OWCs. They're also really pricey... you're looking at starting around $280 for a 1TB.