WWII is my theme because it is the most epic battle yet waged by Man, a true World War, with so many theaters and the coolest weapons. A subject for lifelong study. My future acquisitions will be a Luger, P38, M1 and perhaps eventually an MP40 and if a bunch of money falls out of the sky and into my lap, a MG42.
The Cold War '60s through '80s are also very interesting to me, especially FN FALs, M14s, Dragunovs and by then various HKs such as the HK91, HK93 and MP5.