Rage quit central, and look out because these sorts of parties aren't in short supply. The most irritating parties that you'll come across. Odds are you won't find them all at once, but you may find some of them lumped together.
1. Dude, you're gimping my style!
There's gotta be one of those in every party. You know the type. The ones who'll say "ur armor teh suxor", sometimes they'll go so far to even buy you "new armor". Well, here's a startling news flash, you probably don't know better than anyone else in your party because everyone has their own play style.
Those close to me and myself have all had experience with this type of party.
One time, I even had a party where a member went out of his way to buy me "better weapons" so that I could "deal more damage". I thanked him, swapped to the new weapon, and took it for a spin for about 5 minutes before switching back. The gesture was nice, but I already knew what armor I needed.
The lesson? Know what your classes demand. A DPS doesn't rely on level adjusted weapons, a DPS relies on stat boosts and greater damage. If someone has certain gear, ask the reasoning first before you start saying it sucks. I once had a guild mate ask "Why does X armor add to my enmitty?
2. Time is XP Lost
This applies both ways whether looking for a party or soloing. If you invite someone... STICK WITH HIM! You should know full well how far away someone is before you invite them. If you know that level 10 player you just invited is at least 10-15 minutes out.
If he starts his trek to you, don't turn around and tell him "you're taking too long, we're going to find someone else" because not only did you waste his time, you wasted your party's. You've just wasted 10 minutes waiting for him and you wasted 10 minutes that he could've spent doing something better than trying to get to you.
3. Solo Be, Happy Be
You know those bees poking around flowers by themselves? You only see them together in the hive, well... MMOs have a tendency to be very similar to that.
If someone is solo, don't go and invite them to a party unless you plan to commit. When soloing, players will usually have a different setup of gear and macros than they do when they party. If they are soloing, be prepared to wait some extra time.
Also, don't invite someone to a party if they're not actually looking for one. If they're not looking for a party, they'll slow you down and your party members will become impatient depending on the setup time. You can also lump this in with the previous section. Because solo areas are usually separate from the party areas, there will be down time involved during the arrival process. This isn't a question, it's a guarantee.
4. You're Doing It Wrong
If you're noticing that, then you're doing something wrong. It doesn't matter if you have 500 widgets and gadgets telling you what everyone in the party is doing, if you're noticing someone else's mistakes you're paying too much attention to the rest of the party.
A good party will have a balanced set of dynamics consisting of DPS, Tank, and healers - and that's a highly generalized description. If you're a tank, your primary concern is keeping the aggro. That type you spend to notice the DPS not doing "enough damage" as per your standards is time you could be keeping that healer safe. If they're not doing enough damage, odds are its because they're trying not to pull aggro.
Here's an example from the short time I played WoW. I was in a party with 5 others including my girlfriend at the time. Our tank said to me, "you're not carrying your weight, you need to deal more damage." I looked at my DPS meter and saw myself on top with a total 50k for the night, which was leaps and bounds above everyone else. I told him I had a pet, which was true... it accounted for a good chunk of my damage, but he denied it categorically and rage quit. I looked at my girlfriend's DPS counter, and her's had the same rating as mine.
Don't tell someone else how to play. As long as you're alive, killing monsters, and keeping the aggro off the healer they're obviously doing something right.
5. Life the Universe and Everything
Its one thing to roleplay with your macros - "Is that roasted <t> I smell?" /cast Fireball - its another thing to just go off and start discussing life, the universe and everything in between during the middle of a fight. Where is your head? Is it in life or the fight? Your party seriously needs to know, because if you're not there then you need to have your head examined.
And no, this doesn't apply to witty remarks that may apply to the monster at hand should it have a silly attribute about it. In that case its more of a wham bam thank you ma'am scenario where you give the witty remark and move on.
6. brb, gotta shower
What? Why are you still in my party? Don't do something ridiculous in the middle of an active party. People don't like carrying dead weight. You don't like it, your party mates don't like it. If you need to shower, leave the party. If you need to go to dinner, leave the party. Its one thing if you're eating at the computer, its totally different when you walk away and leave the PT hanging for 30 minutes.
I'll be honest, I have done this on occassion, but this is only when I know for a fact that I have at least 10 minutes to be AFK during. For example, looking for replacement party members in a pick-up party can take a long time, especially in FFXI where your party can look for new members for up to 30 minutes some times with a waiting period of 15 more for the people to arrive.
7. Don't ask, don't tell
It's like the military, except more stringent. No one cares if you gotta do #1 or #2, if you need to go just say "brb - rr" or something like that. Something short, sweet and to the point. Same goes for the aforementioned shower scenario, be tactful with that one - unless you're playing a female character, then you can let the imaginations mostly because there's a good chance that everyone in the PT is a guy.
8. So Long and Thanks For All the Fish
And what better way to wrap things up than with your own closure... When saying goodbye, follow appropriate protocol. Some games may just be "Hey guys, gotta go... I'll catch you later" while others may expect you to provide warning or even a replacement. Just make sure you follow the appropriate procedure. I can't tell you how many times I've had someone just up and leave a party without saying so much as "thanks for the group"... needless to say those are the ones I block.
Back in Asheron's Call, it was common to have an extraordinary number of players in a single group camping a single spot. There wasn't a problem with telling everyone "Bye, I'll cya tomorrow" because odds are it'd be the same people you camp with tomorrow. In FFXI, you let the leader know in advance how much time you have remaining and offer to find a replacement. In WoW, groups usually have a predetermined goal in mind - running a dungeon or raid - so leaving those groups are much easier than other games.
Now it's your turn to speak out. What annoyances have you come across while playing with other players? I'd love to see some annoying experiences that other players have had.