H.M.C. Stands for "Heavy Metal Club". It's a group/club with members who wear colors just like a motorcycle club, and have by-laws and a hierarchy. Most are local while the bigger, more recognized ones are international and have chapters throughout the world.
Dude, the local H.M.C. were all at the show last night in full regalia.
Unlike a catfish who is often a lonely and self-conscious individual, (most often a female), who misrepresents themselves in order to establish an amorous online relationship, a "Spamcunt" doesn't seek your affection, only your money. They are usually social media accounts that are strictly created in order to spam (unsolicited inbox messages/links) you and others with porn site links, often claiming that if you follow the link provided, you will be able to see them nude and performing acts of masturbation for you, for a small fee. A "Spamcunt" is a Porn Merchant.
"Dude, I met this total Fox on Facebook, she is hot!"
"Bro, that's not a real chick, it's a bogus Spamcunt account, dumbass!"