Crocotile3D is a unique level editor that takes the traditional 2D tiled based map creation approach, but applies it in 3D. Crocotile3D is described as:
Crocotile 3D is a tile-based 3d modeling editor. Originally released back in 2015 it is the first of its kind to use 2d tiles to construct 3d scenes. In contrast to most 3d applications that are bloated and over-complicated, Crocotile 3D is a simple to use tool targeted at creating lowpoly models and scenes with pixel-art tilesets or low-res textures. Simply select tiles directly from tilesets and place them into a scene to quickly give them a third dimension. Use various tools to edit your tiles and shape your models, let your imagination go wild!
It is available for Windows, Mac and Linux. There is a free trial version available on Itch.io that is limited to saving less than 100 tiles and cannot export in OBJ format. The full version is available for purchase on Steam. Crocotile is frequently updated, with the most recent release coming just a week ago.
You can see more of this unique tool in action in the video below.