1) Everything involved with /follow, flying and being nearby groupmembers while flying. It's annoying when I have my main (warrior) not getting crusader aura when my pally is flying right on his butt. Also, not being able to take off while /follow. I always have to mount, fly up in the air a little bit, then refollow.

2) A way to interact with NPC's that doesn't involve clicking. Picking up quests is the bane of my existence, even with addon's helping me.

3) Make /follow work so I don't have to feel like I'm driving a Mack truck when I'm going around any turns, stairs, doorways, etc.

4) Mail send delays removed when sending mails across accounts owned by the same person. No trading items around to mail things off to alts.

5) Remove the 255 character limit from macros without having to install an addon.

6) Ability to loot with a keypress, rather than a click. (While interacting with NPC's with a keypress may be a more viable solution, I do understand the exploitation possibilities of adding this in. However, I can't help but notice that bots have already found their ways around it so unfortunately we are the ones that would benefit from it the most, not the botters.)

7) Multi-Character abilities! I'm surprised that no one has mentioned this one yet because it would probably be the most fun thing of all time and not just for MB'ers. Have abilities that require 2+ people to cast it. For instance, two mages could combine their powers to cast Metoer dealing %d damage to all enemies in target area. Or, combine two different classes to gain access to hybrid spells. Something like warrior and pally linking together giving a pally the ability to charge when the warrior does it. Or, conversely, give the warrior the ability to consecrate directly after a pally consecrates. (Hey, it's an idea that sounds fun to me, it doesn't have to make sense yet.) I could go on and on with this... Wrathbolt! Shadow-wrath spell! Combine 2+ durids together and Starfall will hit all targets in range for full damage. OMG /drool

8) Combined character lists. Log into ONE character and all associated accounts would have their characters listed. Once there, you can log in directly or launch another wow client with a specific character. Let's face it, we spend enough money to keep the multiple accounts going, whats the harm in being able to log in on multiple characters on the same account given that we "have" the licenses to do so. I own 5 accounts. I want to be able to log in 5 different characters. They are all owned by me, why make the extra distinction?

9) Mini-Window mode. This is less for MB'er but more for anyone using windowed mode. Have a way to shrink the game window to a smaller like taskbar box. (Think Windows Media Player style or Vista Pre-View, only a little larger) When in this mode, it uses less system resources. Here's why I want this, because if I want to go to wowhead, allak or any other WoW website, I get slammed a lot of times in the minimize/restore/crash/displaywon'tupdate/etc. Not really a computer specific problem because running 4+ copies of WoW on one good computer would be equally better than running 1 copy of WoW on a crappy computer. Add into it something where you can press a button that switches from full screen to a small windowed mode to access a webbrowser, then press a button to return to fullscreen. Do this without having to deal with a windows key to force it's way out of fullscreen mode.

Give me some more time and I could probably come up with some more, but I think this could be a good start. Not expecting half of these are possible or likely, but some are fun.