Oh my.
Let's see, where did I start...
I think it began for me with MU Online - I had a Dark Mage and an energy-build Fairy. After getting bored of the Mage (and picking up a rather handy hacking program that allowed me to double up my attacks per swing) I made a Knight and shot up to around level 80 - out of 400. I dropped that.
Priston Tale - holy crap I want to play this again, but I refuse to pay for any MMOs besides WoW (we'll get to that later). If I could find a decent private server with bumped up rates (maybe 5x more exp) I'd never see the light of day again. Pikeman and Priestess classes, both of them promoted on the free-beta before they made you have to pay to play a character over level 40.
Ragnarok Online, and how. Started this back in late '04 and I still play it today (just logged off the current server I'm on a few minutes ago). This was in fact the first MMO that I've wanted to play - back when 2-2 classes had just been released (half of their jobquests weren't implemented - just get to the right level and talk to the npc, BAM instant jobchange.) Now, 5 years later, I've gone from a 3x/3x/2x server (thats base experience, job experience, and drop rates) to a 75/75/50 server. I don't have the time to be grinding ceaselessly for little reward; this server promotes the fun of the game for me. I typically play caster-style builds - Scholar (soon to be a Sorceror), High Wizard/Warlock, High Priest/Archbishop, battlebrewer Alchemists. The Homunculus system for the Alchemist class has my heart hooked. My bored little sheep will tank an entire map's worth of monsters for me without breaking a sweat, as well as the explosives I lob at said mob. Little bastard has more HP than I do. Playing as a Priest class, I dare say I'm one of the better Priest players on the server, compared to the mass majority I've seen roaming around. Especially with an Archbishop - they have so many reactive, preventative, and finally combat skills that they shouldn't be standing around waiting to heal someone.
Also, final note on RO, Shadowchasers are bloody fun. Copy two skills that belong to other classes, autocast them on attack, ability to use bows, remove other players' gear, and sneak around in peoples shadows - literally? Please, YES.
And then there's WoW.
.... Eh. Horde. Not fond of Gorefiend, a PVP server, cuz everyone there foams at the mouth and is like RAAAID, ENDGAME, PVP, ARENA RAEGRAEGRAEG. I prefer a more mellow server type - like Steamwheedle Cartel, RP. I don't usually RP there, but if I find an intelligent guild I'll come up with a flimsy story and be a supporting character for someone elses' RP.
On WoW I'm always the healer. Resto Druid, Holy Paladin, Resto Shaman. No Priests, can't stand levelling them :C too squishy. I also enjoy the occasional Prot Warrior.
On Ragnarok, though, Priesting can only go so far for me before I pass out from ennui. The high level areas don't need healing, just buffing - if you can fight there, you either have enough HP to shrug off the hits, or you have enough dodge that nothing hits you. A Priest just stands around and heals once every few moments, no real challenge. Instead, I play my Warlock, Creator, and Shadow Chaser more.
I'm good for supporting people - I love being the one responsible for that last second save, the one who prevented the wipe. Ragnarok just doesn't have that much danger though, cuz the classes - while varied - are overpowered at high levels.
If anyone wants the RO server I play on, PM me. I dunno the forum policy on declaring private game servers, and I'll err on the side of caution.