Deomonbane is a visual novel that mixes mecha and lovecraft into a badass combination.
Humanity has started to delve deep into the forbidden secrets, making magic a subject that is studied by science and taught in certain exclusive academies. Our protagonist left one of these under suspicious circumstances and is then hired by a rich heir of a big corporation to find a tome with enough magic power to activate the Deus Machina the company has constructed, Demonbane.
This VN has it all, many giant robots, evil magicians with guns, swords and whatever else kind of weapon you can imagine, eldritch powers, outer gods, rape, muscles, manly friendship, mad scientists, humanoid books, reality breaking powers, tits, cyborg batman with tits, androids and normal people that are still pretty badass.
It has it's flaws, both on the technical and story side, but it's still one hell of a ride and you should at least play the Al Azif route if you are into VNs.