From the start you have a unique 1911 with a glowing iron sight. The M4A1 you also have from the start is unique too because it has no iron sights unlike multiplayer which has them folded.
Your allies can drop unique variants of M4A1’s and EBR-14’s that can have muzzle attachments that don’t exist in multiplayer.
EBR-14’s can have bright and less bright red lasers despite the fact that you can only put a tac laser on it in multiplayer. They’re pretty interesting to hipfire with.
M4A1’s can have parts from “Zip Tie” blueprint and a GI mini reflex without its optic raiser unlike in multiplayer.
And that’s all I could find for now. There are still some honorable mentions that I would like to include in my future posts but they need video demonstration. Let me know in the comments if I missed something!