Your Halloween outfit so screams Counter-Strike to me, and I've logged all of 10 hours tops in my life playing CS1 and CS2. (Now I've played maybe 10-20 additional hours of this one CS mod from years ago, God what was it called ... something where you had humans vs. aliens? and they could upgrade? so you had marines with jetpacks like the Rocketeer? and the aliens went from being crabs to being velociraptors to being giant rhinoceri?)
Anyway, yeah: Counter-Strike.