The Dagger of Xian from Tomb Raider 2. Foam core, paperclay, rhinestones, ribbon, spraypaint, etc. This was my entry in the 'By Hand' contest on the Eidos TR forum.
Update 11/7/12: I have closed my own cosplay site due to lack of time, but the tutorial for this prop can be found at [link]
The dagger itself is now part of Meagan Marie's collection. I gave it to her when we met at New York Comic Con. I was excited to hear she might actually use it for her Steampunk Lara costume since her original dagger unfortunately was damaged. [link]