Hey I'm one of the designers of the game. In Killer Queen the only middleware we used was 2DToolkit for 2D rendering, although this is no longer necessary since

Hey I'm one of the designers of the game. In Killer Queen the only middleware we used was 2DToolkit for 2D rendering, although this is no longer necessary since Unity has 2D tools built in. However with other projects, especially 3D ones, I use stuff from the asset store all the time. Some of the code we're using from the asset store handles pathfinding, procedural terrain generation, tweening, and GUI rendering. Plus, we get a lot of art assets from there (especially for placeholders.)