It's been proposed before that the correct plural noun for a group of FedSunners is a "blessing." (Though others contend that is is, in fact, a "curse.") It seems to me that there should be such nouns for other factions, as well, so I started making a list. Falchion is responsible for at least half of it.
Fed Suns - a blessing/curse
Lyrans - a gross
Free Worlds - a parliament
Capellans - a working party
Combine - a ******
ComStar - a conspiracy
WoB - a scourge
RotS - a derangement
Clans (general) - a horde
Mercs - a billfold
Outworlds - a hayseed
Taurians - a paranoia
Canopians - an orgy
Marians - a fiddle
Rim Worlds - a bastard
Star League - a gilding
And last, but not least, a [REDACTED] of Wolverines.