The Person Who's Just There for the Free Drinks
This person doesn't even know what the event is for; they were forwarded an email in which an open bar was advertised, and they jumped at the opportunity. They won't tip the bartender, but they will ask him for an extra drink for their "friend," then quickly chug it to avoid the embarrassment of being caught double-fisting.
This desperate individual will also post a photo of their poorly-made cocktail to one of their social media accounts and hashtag the alcohol brand. Count on this person to sniff out marijuana smoke with the enthusiasm of a 15-year-old and act like they just freebased OxyContin after one hit.
The next morning, they will tweet about how "crazy" the night was, and post a picture of themself doing an overly-calculated pose in the back of a cab with their struggle friends.