actually I'd be quite contempt with a normal collector's edition that has an artbook (at least 150+ pages and the size of a book, not a CD case *winkwink*), a CD with the soundtrack
now seeing as it's the last part of a trilogy it could include all three soundtracks, a complete artbook spanning ME to ME3, and the above posted complete codex looks actually very neat
- concerning models of weapons, there might always the question which one to please alot of people? sadly a (wearable?!) replica of an omni tool wouldn't work so well due to the transparent and glowy nature of the omni-tools
- a statue of male Sheploo... you don't want to go there, I believe

- it's a shame Nihlus lasted like what... 10 minutes? a detailed statue (not an action figure) that actually looks true to the character might do it
- on a less serious note, how about a shifty looking space cow piggy bank