There aren't many interface mods out there for Guild Wars (since it's not natively nor officially supported) so this one definitely stands out from the crowd. The design is based around flat strokes and a reflective body. Comes in two color schemes: Graphite (top frame) and Classic GW (lower frames).

Using this mod requires an additional program, see here for instructions.

6/16/08 Update: Version 1.1 is now out. Check the release thread for a changelog.