Duality
Duality is a third-person action game (like Oni and Strident), which (like Strident) was developed by Phantagram a.k.a. Trilobite Graphics and (like Strident) was eventually canceled despite being rather promising.
Trailers
There are two trailers. Neither of them is anything to be overly excited about.
The first is almost unavailable online in its full version, the only place I found is HERE. IGN has published it in a somewhat dismembered form (6 segments dated April 8, 2002), labeling it "Gameplay" although the trailer is clearly staged/rendered (the IGN segments are here: 1 2 3 4 5 6). The trailer follows a Hacker (she) and a Mercenary (he) as they break into a heavily guarded facility, steal some important stuff, and then escape.
The second trailer is higher-resolution and shows some actual gameplay (mostly stealth), as both the Mercenary and the Hacker make their way through enemy territory: Duality [XBOX Trailer Action/Stealth - CANCELLED!]
The final sequence of that second trailer is a hint at the third playable character - the "Virtual Being". Apparently it plays chess.