You would be astonished to know how early (decades ago) this was reviewed/considered. Long before the treaty outlawing warfare in space we were considering a titanium rod which would be spun up and ejected to any target on earth.
There is a very large and very classified group of researchers working to figure out how every new invention can be turned into a weapon of some kind. I have seen tungsten rods dropped from space — last I knew they were not very accurate. But these hellfire based missiles have guidance systems so they literally can hit a spot on the vehicle. The other thing we do is add kinetic energy by flying into the target and we can have a large range of explosives varying to no explosive at all. It all depends on the mission. Needless to say, there are some places where this is exactly what you want.
Tungsten. Titanium density (kinetic energy) is too low.