This was an electrical panel I did for my latest project Mad House. One of the big takeaways from this project specifically was figuring out how to make complex looking pipes with a relatively low polycount.
Also for Mad House, I made a basic fan. In an effort to keep the polycount low I beveled the edges visible to the player to make it look as realistic as possible. For the pieces not seen, I kept things pretty basic. I also kept the fan blade as a separate piece so that when it was imported into Unreal the level designers could player with the blade count for slight visual variation in each room.
Also for my current Project Mad House. For this project we had to show the asylum changing over time. This filing cabinet was to be stored in the maintenance room around pipes and such. So In substance I used a generator for rust that I could scale at any point in time. The model on the left would be what the player sees in the early years of the asylum while the one on the right is what they'd see years later.