There's 3 mandatory things:
-Hardback artbook (not a shoddy PDF)
-Soundtrack on CD in at least a jewelcase (so not in a cardboard leaflet, and not some "digital download")
-The game itself.
Ideally, a metalcase with specific notches both for the game disc and the soundtrack CD.
Maps are more for fantasy games, and even then, only if they correspond to the ingame map and are made of cloth instead of glossy paper with folding lines all over. (The early Ultima games got it right!)
A diecast figure or vehicle model would be neat, but isn't really necessary in my opinion.
PDF artbooks and soundtrack downloads have no place in a Collectors Edition. They're stuff for Digital Deluxe version.
DLCs, I'm fine with those. Really, I have no problem with a day-1 DLC being included in the special versions, while made available for sale to owners of the regular versions. Provided the DLC is not cut content, but really optional additional content. (This was done right in the Dragon Age and Mass Effect games so far, the games did work perfectly without those DLC's, I found no cases where DLC content was referenced or required to proceed through the storyline.)