Haven’t seen a comprehensive master list yet, and seeing that the time is near, I thought I should make one up. Any edits, additions, or errors, let me know and I’ll fix the OP.
All editions of Halo Wars 2: Ultimate Edition will come with the Halo Wars: Definitive Edition download code. The Ultimate Edition will also be released in the US on Friday, 2/17/17.
Best Buy - Limited Edition Merciless Variant Atriox Figure, Decimus Pack (link here)
Microsoft Store/Xbox.com - Professor Anders Pack (link here)
PC Richard - Collectible iron-on Patches (link here)
EBGames - Shipmaster and Atriox Pack, and Xbox Controller Stand (link here)
EBGames - Shipmaster and Atriox Pack, Red two pin pack, and Steelbook (link here)
That’s all I could find doing some quick searching and rounding up, let me know if you know of anything else!