The Damsel
Undeniably plucky of character but ultimately ineffectual excess baggage that constantly needs rescuing, reviving, retrieving and/or resuscitating. Co-op 'damsels' have none of the redeeming characteristics of the traditional 'damsel in distress' image. That is, they aren't vulnerable maidens all tied up and waiting for a hero, but are just men that aren't very good at games.
The Slow Reader
Recently made unpopular thanks to the likes of Resident Evil 5, Gears of War 2 and any other co-op game that likes to leave journals and diary entries scattered about. Slow readers love to read absolutely everything. Slowly. And sometimes twice. They believe that taking time out during an intense shooter to properly digest several screens of text is an integral part of the experience. Literate people have never been so annoying.
The Glitch Finder
Ignores the game in favour of accessing supposedly inaccessible areas and generally trying to exploit broken bits of the game to their advantage. This means that they spend all of their time bouncing up and down on bits of the environment like a demented jack-in-the-box and generally behaving as though a fairly essential section of their brain has been removed.
The Blamer
Suffers from a complete inability to admit personal culpability, instead choosing to finger-point and fabricate mistruths to cover their own ineptitude. Blamers are masters of creative bullshitting and can effortlessly deflect accusations of weak gaming skills with frightening efficiency. Typical favoured scapegoats of blamers often include: inadequate co-op partners ("f***ing noobs"), technical deficiencies ("f***ing lag") and acts of God ("f***ing swarm of killer bees").
The Mute
Very reluctant talker. Sessions with a mute can be surreal affairs, often tinged with a pervading sense of creepiness thanks to the deafening headset silence. A mute will occasionally offer a primitive mumble, grunt or noisy nasal exhalation. Actual spoken words are extremely rare, monosyllabic and only uttered when a lesser form of audible communication isn't effective enough. Has less personality than an AI team-mate. Feels like playing with a stalker.
The gobshite
The motor-mouthed antithesis of the mute. There are plenty of friendly, good-natured gobshites out there that just like to natter, but we're not talking about them. We're specifically talking about the smack-talking gobshites that relentlessly vomit unfunny and offensive mouth waste. They might be able to nail a headshot from a hundred paces, but there's no fun in winning when you're teamed-up with one of these nasty little sphincter stains.
The Griefer
Playful jokers or irritating twats? If they're 'playing' on your side then they do, without doubt, always belong in the latter category. There's nothing like being on the wrong end of a griefer's pranks to make you rage like a mental pissed-up wasp with hypertension trapped in the world's most cramped jam jar. It can ruin your day. Conversely, to cheer yourself up again, watching griefers making other gamers' lives a misery can be quite the tonic. Strange.
The Lone Wolf
Completely oblivious of and inconsiderate to other players. Their actions are dictated by their own needs and whims. They selfishly grab all the best pick-ups and have absolutely no hesitation in abandoning team-mates. They never listen to tactics and don't have even the faintest interest in playing as a group or partnership. A lone wolf firmly believes that 'team' is spelt 'teiam' and thinks 'co-operation' is a surgery-based board game. An example of this is the infamous "Leroy Jenkins" from the online game of World of Warcraft where Leroy runs into a large room full of dragons despite his teams tactics ultimately killing them.
The Drill Sergeant
Likes to shout a lot and is intensely serious. Plays like there are actual real human lives at stake. Pretends to be well acquainted with the fundaments of tactical military manoeuvre and loves barking things like "FORM UP PINCER FORMATION!", "EXECUTE FLANK MANOEUVRE!" and "LET'S HIT 'EM HARD PEOPLE!" at bewildered team-mates. Would almost certainly be scared shitless if they actually went within 100 miles of a real-life war zone.