Gamma would be cool. Almost like a mix of photons and neutrons. I could see it being useful, although Alpha and I-forget-the-other-type would be excessive. I mean, Alpha is only a weak version of Gamma rays.
Neospector Yes, gamma seems to be cool. I'm agree, smth like mix of PHOT and NEUT, but passing through everything. And like kamikai said, it will be nice with green glowing