Custom Sword Smiths

Ben Potter is a creative sword smith who's passion for turns swords into individual works of art. He has two websites for custom swords:
Privateer Armory
Cedarlore Forge

Custom Sword Smiths with good reputation are:

Kevin Cashen, 
Michael "Tinker" Pearce, 
Al Massey, 
John Lundemo, (http://www.odinblades.com/)
Craig from Arms and Armor...

I'm probably missing a few here too.

The big question is what do you want it for, and how much are you ready to spend? For example, if you're looking for a WMA sword that can withstand a nuclear blast but still remain balanced, I'd suggest Jean-Philippe Henry of the Heimrick Armeor, where you can get a decent WMA sword for about $250-300. If you're looking for a historically accurate cutter, you're probably looking at around $1000 plus; a less expensive option may be to take a Gus Trim or Albion blade and have Christian Fletcher make a custom hilt for you, but you're still looking at upwards of $800 and up once it's all said and done.

For medieval/fantasy style swords - Brendon Olszowy from Fable Blades is easily one of the most skilled and yet affordably priced modern day sword artisans around who takes pride in his work.

Cedarlore Forge

http://cedarloreforge.com/