Artstation - CityKit: Sci-Fi Edition Part 5 by Joost van Kempen

https://www.artstation.com/marketplace/p/6Gp7/citykit-sci-fi-edition-part-5

Part 5 of the best selling Citykit series, these are kitbash packages for creating sci-fi themed cities quickly to help you with your illustrations/matte paintings etc.

OBJ | Zbrush Files

https://www.artstation.com/marketplace/p/PL6a/citykit-sci-fi-edition-bundle

This kitbash set contains:
13 high poly models (.OBJ and .ZPR format)
13 low poly models (.OBJ and ZPR format)
13 decimated models (.OBJ)
Bonus 7 high poly models (.OBJ format)

Artstation - Blender - Sci-Fi Remote Tutorial

http://www.artstation.com/marketplace/p/5jp91/blender-sci-fi-remote-tutorial-using-add-ons

Do you want to learn Blender with industry standard Hard Surface Add-Ons?
In this tutorial I'll show you how to create this Sci-Fi Remote from start to finish. I'll demonstrate my modeling process and cover how/where I use add-ons like BoxCutter, HardOps, MESHmachine and MACHIN3tools. After we finished the model, I'll use DECALmachine to add details to the model.
You need to have basic knowledge of Blender but beginners should still be able to follow along easily.
MACHIN3tools is FREE add-on, however, BoxCutter, HardOps, MESHmachine and DECALmachine are PAID add-on.

Artstation - Vintage Sci-Fi Pack 80+ Smart Materials

https://www.artstation.com/marketplace/p/jNlN/vintage-sci-fi-pack-80-smart-materials

ArtStation – 15 Sci-Fi Solar panels pieces