If you guys want to get into Gmod, I reccomend some server with Wiremod and ACF (Armoured Combat Framework). Wiremod recently hit the Workshop (no incremental updates, but it works), but ACF needs to be retreived from a repository still.
Wiremod: If you haven't looked into it, you should. It allows its stuff and that of other mods to input and output values, allowing you to... wire electronics in things... It really improves the number of things you can build, and the quality of the result.
ACF: A framework for props to take damage, ballistics/penetration/ricochet calculations, a slew of guns, an engine and gearbox system, cool explosions, Wiremod integration... basically everything you need for vehicle/drone combat in GMOD without making everything out of wood.
We could spend our time building huge, stupidly impractical Dwarf-tanks and blowing each other up! Planes too, if the server has Fin tool (simple aerodynamics simulation) and you suck less than I do at building stable propellers.
Alternately, Wiremod and Spacebuild is another great combination.
Spacebuild focusses less on damage and propulsion and more on resource management, and is designed for spacewars rather than building tank replicas.