You are allowed to use whatever you want, however, maining a shotgun or a fusion rifle for a whole match gets on my nerves - it's not the fact that they're overpowered or anything like that, it's just really frickin' annoying (sends off a vibe of "I can't kill shit unless I'm using a 1-hit-killer"). The one thing I do hate on (all the time) regardless if you're switching weapons is the SUROS Regime, screams scrub/tryhard.