I'm really bored, so why not...
edit: IN MY OPINION...
Mercenary
Pros: Best all-around fighting class. Period. You are by FAR the most versatile. You might not deal as much damage as a furied barb, and you might not dodge/parry 100 attacks in a round (though shield block can help), but you sure as hell have the most reliable damage output/defense (eparry+specialize) and the ability to hit everyone in all rows (trip, reaching weapons, bows). No leet tracking, but in exchange you get retreat... the best defensive group skill. Period. All else being equal, I would trust a merc more than any other char to hold and lead a group. When a merc is fully spelled up, there's simply NOTHING that will drop him short of petrify/fod (and he should have plenty of fort to counteract that). Overall, this class is FUN to play. There are so many options available to you in combat and so many strategies, unlike barbs/swashes.
Cons: You're reliant on items/other characters. A merc who wasn't specfically preparing to beat a swash would get absolutely destroyed by one in pk. Plenty of things can still kill you- warlocks, for instance, if you don't have a SS breaker. Sorcs. Necros. Even priests with a good sanctuaried pet in front of them. Mercs are all about the buffs- at the very least, sanctuary. You should always keep gs/haste/di items on you at all times, at the very least. Next up are SS, RE, amor, shield, protection. If you pk without items, you're losing out on just how dirty this class gets when it reaches its max potential.
Also, reliant on EQ. Armor somewhat, but weapons ESPECIALLY. The best specced weapons are usually rare in their adamantite/energy forms, so you have to constantly fight with other people to get decent weps. If you dont believe me, give a GM merc a non-specced bastard sword and a shield and watch him fight ANYONE. It's pitiful. It takes me like five rounds to kill the bats in morea.
Swashbuckler
Pros: Perhaps not the best all around defender (shield block > parry all around) but certainly against parryable weapons. We've all seen logs of swashes against necro armies dodging/parrying every attack in a round. Swashes are good spelled up, yes, but they're not as reliant on it as mercs, especially since most of them already have dexs near max (haste isn't as crucial). You can taunt and drop a caster by what, 7 points with max cha? Something like that. You are the ultimate anti-warrior. I've seen sprite swashes taunt mercs and literally shut them down for the fight. assuming "i win" spells don't land, there's no faster way to completely strip an opponent of their melee damage capability. You don't need to do jack in combat and still do a decent job.
You really can't foul up being a swash. Just hand them a suit of mithril and two good, accurate, fast weapons, and their automatic skills take care of the rest. They may not be as elite as in the hands of an amazing player, but they'll do their job.
Cons: It's boring as hell. After you taunt, you have three options- disarm, dirt or trip. Disarming works 1/5 times on one-handers, 1/10 on two-handers. Tripping won't work assuming your opponent is even halfway prepared (quaff lev- gee, that was hard). Kicking dirt is all right, but that forces you to land and be open to trips, though most would just bash you. Basically, swashes are very mindless IMO when i played mine. Battles are just the eternal kick dirt/disarm attempts. You lack versatility, reach (haha landsknecht you're funny), range (crossbow + 2 attacks=sawk), and basically things to do. Most of your skills are automatic.
Also- you can't deal damage. People have said this is simply because i'm always wearing heavy armor (duh) when they attack me, but my response is... who ELSE would a swash be attacking? Swashes, especially against shields, do nothing. That's not their job. The commonly thought of best pker swash in the game was doing 3-4% a round to my adamantite with no spells up and a pike. Then there's ripostes, of course...
Oh, did I mention that you can't kill anyone? Dying (not losing, DYING) to a swash is disgraceful. Anytime you're losing the battle, quaff word. What are they going to do? Trip you while you're flying/mounted/being a pet? Taunt you? The inability to bash makes their kill rate far less. Swashes win battles- mercs/barbs win wars. You could completely shut down a barb/merc in a battle, but he'll just be back later and hunt down everyone in your party, bashing them and killing them one by one. You lack that ability.
Barbarian
Pros: Less combat versatile than mercs, but more versatile outside of combat. You lose out on trip/eparry, usually encouraging barbs to go straight damage with accurate damaging two-handers to take full advantage of the fury speed bonus. Alertness/counterstrike/toughness sort of balance out a bit the lack of defense- but i'd still, in general, rather have a merc over a barb in a fight.
However, you get TRACK. People are stupid. That's the long and short of it. You should always be flying everywhere, but people aren't. You can get so many kills by just making runs of the portal stones till you find somebody. It really doesn't take that long. Just track them down, eat a haste herb, run in and bash. It's over.
Cons: Less combat versatility. You also take more damage in combat on average then swashes or mercs. If you have a shield this helps offset the lack of defense, but you're WASTING your fury speed bonus. Slow damaging weapons benefit more from speed bonuses than fast low damage ones because they deal more damage per hit. Fury+haste=damage machine.
Just like swashes, IMO barbs have less potential than mercs. In the hands of a halfway good char, they can be decent chars. however, a major skill like toughness is USELESS to a great player because they'll always have the best adamantite. Also, good players will usually be starting combat so counterstrike gets a wimp. Constant DI/DH of prepared players negates alertness except for camo/sneak, which aren't used enough to really be worth it.
Priest
Pros:Starting to move past PK here, i guess. Priests have a lot of RP that just gets thrown at you, whether you like it or not. Ressurections, faith rp, etc. etc. In Pk, priests are of course the best defensive support chars. Heal+sanctuary, mass heal when blinded by dirt. If you like helping people, priests/sorcs are a good choice. You also get the best all around damage spell in the game- harm.
Cons: Priests are surprisingly well rounded chars. They are no where near the frail chars they are in other games. Sanctuary+protection+armor+shield block+magical vestments/heavy armor= great tankage. Bashes will still end them though, of course. I guess a con would be the need to constantly be behind something- pet or PC.
There are others cons but I can't think of them
Paladin
Pro: Tanking beast. Especially against darkies. Mercs will do better if a GM casts sanctuary on them, but paladins can hold it themselves. A cross between a mid-level merc and a mid-level priest, they get call armor and BoG to seal the deal. NEVER underestimate a paladin's ability to live. I've seen necros bash one with an army, start casting fod, only to have the paladin shrug off the bash in time to holy word all the undead to death. Against grays, bring a GM merc or GM priest. Against darkies, especially priests/necros, none better than a paladin to do the job. I trust paladins to tank so much they're one of the few classes/NPCs I will stand behind and depend on to live.
Con: You suck against grays. Pure and simple. You can still win if you don't get bashed (cure light in between rounds) but betting on not getting bashed is a bet you'll probably lose. You still get three attacks, you still get sanc, you still get shield block, parry, etc. etc. but in gray fights you basically just cure light in between rounds and wait for someone to end the battle. You're not an integral part of the fight- just a placeholder.
Hellion
Pros: Rogues might be able to drop all the classes in the game except barbs/mercs/pallies in two backstabs, but a hellion will get all of those. Sneak/invis/hidden = best natural stealth set. Cleave is decent- i'd usually start with o all bash if i knew i was going to win the fight though. The one round lag on cleave is more then enough for them to escape.
Let's see... you can dominate mentor level mercs and give em eq. You can cast all the maledictions except sleep (and with art they are now the best spells in the game), 4 of which go on your weapon. Hellfire is a great all around damage spell (imagine BoG against anyone without the nimbus), and it'll toast centaurs/elves. It even works against RE to some degree. You also can make the best invasion routes in the game (rifts).
Cons:
Don't be a fool and stand in the front row. Always be behind at LEAST your nightmare, preferrably a dominate. Constant maintenance of charms is of course, dangerous. Also, the amount of stat mods you need to get is SICK. Cha/int/wis/str/art must all be maxed to gain the full benefit of the class. You will find you much resemble a caster class then a warrior one- no parry, no shield block (all good cleavers/reach weapons=two handed), defensive spells are spell oriented (shield, protection to some extent). You're amazingly frail to melee damage (mercs with reaching weapons in the front row will rip you up) so keep people bashed/blinded and make sure you always start fights. Don't cleave barbs.
I'll do the rest later.