Something artillery-ish would actually be nice, if done right. I always liked how the projectiles go straight up then straight down rather than horizontal. If I were a C&C Generals General, I'd be an artillery General
But another idea is a weapon like the Mirage Tank's weapon - I always thought it looked more Soviet than Allied. It actually looks like something Iron-Curtain-ish of you ask me.
Yet another idea, is a kind of weapon that remains constant - that is, something like a beam or machine gun; not a delayed kind of thing like Tesla Coils and Prism Towers (and most other weapons in the game actually).
Just some thoughts.