Mechanical keyboards represent the high end these days, but they're fairly pricey. I currently use a Nighthawk X9 from MaxKeyboard, which uses Cherry MX Red switches, and I love it.
I can't say it's the best keyboard, but I can't think of anything on the market that is better. You can get it with red or blue switches, which dictates the key resistance, and it has full accurate backlighting, as well as anti-ghosting. You can read my review on it, here.
Not sure what the best Keyboard would be. But I use a simple GearHead Keyboard and I have no problems with it. For me, the more simplistic it is, the more I like it.
I cannot stand the "bubble" keyboards. Any keyboard that is flat is the best keyboard, to be quite honest. One with a numerical pad is also pretty awesome.
A flat, backlit keyboard with a numerical pad is the best keyboard. 😛
I had a Microsoft Ergonomic keyboard that I really liked a while ago because besides being ergonomic it had soft pads for your wrists, keys were fairly "clickly" (I hate mushy keys), and it was large which I think made it more comfortable since you had more space. Might get one again but I see the price has went up a lot of course. 😛