Duelist

Although Obsidian has not confirmed it, the Duelist prestige class appears to be included in the IGN Preview video release May.

DnD 3.5 Duelist
Description:

Requirements
Base attack bonus: +6

Skills: Perform 3 ranks, Tumble 5 ranks

Feats: Dodge, Mobility, Weapon Finesse

NWN comparison
This class didn't exist in the NWN.