Are props/weapons a factor in Deployment (I keyword-searched through all four pages and didn't see anything on it)? If the answer is "yes", that question breaks down into two specifics:
1) If someone's cosplaying a specific Halo character (let's say Halo: CE Master Chief), rather than just "an ODST" or "my multiplayer Spartan", and has a prop weapon to accompany the costume, does he/she have to be using a gun from that game, or could he/she be armed with something from, say, Halo: Reach or any other Halo game that isn't Combat Evolved?
2) Are weapons from other properties permitted, even as secondaries (like if I had the Avatar AMP suit knife as my character's knife in a sheath somewhere on my body, rather than a UNSC-style knife)?