While I am of the mind that airsoft is no different than the LARP guys who run around with swords, I have to agree with most people here.
LARP = Live action role play. We're not soldiers, we're pretending to be in a game that we play outdoors in real life. Dispute it all you want, we're just wearing different costumes compared to the kids running around in the woods with swords. Unless it's a sanctioned military event, and you are a serving member, your nice CIRAS and drop leg holster, fancy camo and gloves are just part of a costume.
That being said, most games have an agreed upon feel and scenario even if its not publicly stated. Even period correct stuff is really off the wall depending on the era. If you show up with a muzzle loader replica in full civil war regalia, you are going to stand out in most games. Even with a WW2 load-out in some cases.
There ARE games where non-standard kit fits in awesomely, mainly Halloween and special "goofy" scenarios. Hell, i work some HALO ODST stuff to a Halloween game as I was a special character in the game. Would I wear it to any other game? Not likely, no.
TM G36, KSC USP, borrowed P90 and a really big L96