TerraTech (https://store.steampowered.com/app/285920/TerraTech/) for the vehicle building category. Very streamlined and surprisingly deep, although the campaign gameplay can be frustrating.
Workers & Resources: Soviet Republic (https://store.steampowered.com/app/784150/Workers__Resources...). A planned economy city builder. It's apparently an extremely deep game with a steep learning curve. Seems to have developed a cult following.