Kensai

[hivedragon]

What weapon makes for the best signiture weapon?
What enchantment would you suggest for each level?

[Rossebay]

Start out as Exoticist Fighter and grab the Fullblade, Spiked Chain, or Elven Courtblade.

Or a Kaorti Resin Jovar.

Really, whatever weapon you get, make sure it's Kaorti Resin, really. That may require an extra proficiency (exoticist gets 4, so no worries there).

For enhancements, I'd say Metalline (a +2, from Underdark, a Faerun book), for those just-in-case situations where you can't overcome their DR. If your DM wants to use the Metalline enhancement in the Magic Item Compendium, then instead use Shadow-Striking (+3 Enhancement).

It's a nice step up. The original +1 would be a boring old damage enhancement.

You can trade out enhancements at each level, right?