Cube

Cube is a freeware 3D first-person shooter game. It can be played both in multiplayer and singleplayer mode. It allows the player to edit maps in-engine in full 3D, this means it is possible to fly around the map, point and drag to raise/lower blocks, create slopes etc. Multiple online players can even edit a map simultaneously.

Cube is heavily influenced by Quake and it is the predecessor of Cube 2: Sauerbraten.