I would like to submit the following items. Sadly most of these are headcanon as his canon doesn't give him much really.
-Childhood Photo of Alex and Dana before Alex moved out.
-Gentek Labcoat (Embroidered with Dr. Alex Mercer on the pocket)
-Alex's notes from Gentek, working on the virus.
-Dana's laptop with all her findings from the unraveling of the conspiracy until she gets kidnapped. (This last one is canon, but isn't very important once Dana gets kidnapped in game.)