I thought that I'd make a list of my addons to give other people suggestions, but to also get some ideas (via comments) of what other people like for addons. I'm sure that I'm missing something, but I'm pretty happy with what I have right now. Here are the addons I use the most with a link to where you can download them.
AuctioneerIf you like making money on the auction house then this is just mandatory.
PetEmoteI love this mod, if gives your pet a voice, weather its a pet for hunters, a demon for locks, or a ghoul for DKs. This mod is especially important I would imagine if you roleplay.
SmartBuffI'm an idiot. If I don't have something to remind me to buff up, I'll forget. Mind you who's a hunter going to buff, but my DK's bone shield thing is constantly going up. So this is mostly for my alts. My wife loves this mod with her mage.
SexyMapJust added this one, I'm not sure of all the features besides the sexy animation that is around the minimap.
CartographerNice map mod, I love that it includes the dungeon maps. There is a lot of features of this mod that I don't utilize. Sad I know.
Quest HelperThis little mod has changes all of our lives. Of course in Northrend it doesn't always get it right. Can't always trust Quest Helper (like the time it told us to go to Nagrand to assassinate that one guy instead of Borean Tundra /shakes his head at his own stupidity).
GathererIf you do any flower picking *herbalism*, or mining, this is a must for you.
Kharthus's Hunter TimersThis mod keeps track of timers for me. Like my serpent sting, lets me know when I last put it own and how soon I'll need to refresh it.
ItemRackThis is a nice little mod that will let you change your outfit quickly. I haven't had much use for it, but someday I'm going to level that Druid, and by golly I'm going to have at least a couple sets of gear on me. This mod (or one similiar to it) will especially be helpful when we get into duel specing (unless Blizz adds some feature to the game like the hinted about).
MinipetThis mod will remind you to pull out one of you noncombat pets, and gives you a button to do so, randomly. I'm a dork, I love this mod!
MountifulBasically the same randomness of Minipet, but with your mounts. As stated in previous posts, You get to the point where if you have too many mounts (I have 60 now!) then you can't fit all of them into a macro *even if you are using numbers instead of the names of the mounts*.
Omen Threat MeterGotta keep your aggro down. I've heard it said, if you aren't being forced to feign death then you are dpsing enough. Here is your aggro meter so you can make sure that you don't pull from the main tank.
SKG *suicide kings*This is our guilds current system for distributing loot. Its designed for a casual guild, but I think we are going to more of a traditional DKP system sometime in the future. I for one like SK more because I'm more casual and I'm not punished for it.
Deadly Boss ModsI love this mod, it helps out in all of those nasty boss fights. It gives you useful stuff, like telling you when the next phase of the fight is coming up, when you are suppose to spread out, when are suppose to hold still, etc, etc. All of that junk. "Don't move - Flames!"
ViperWatchThis is a Hunter only mod that gives us a little reminder to turn your Aspect of the Viper on when your mana is down and turn it off when your mana is back up. I don't know how many times I would forget to turn the d@mn thing off!!! The funny thing is the sound that they use for this particular reminder is the same sound when you failed a quest, so at first I was always thinking, "crap I failed something, what did I do". But now I'm use to it so it's no big deal. This is a must if you are a hunter, not so much if you aren't. There is another one called
ViperNotify. It looks like its more popular according to Curse Gaming, but I haven't tried it out.
Little Black BookI just got this and I haven't played with it yet. This is particularly nice to have on a PvP server. It is a kill-on-sight mod that keeps track of the Horde (or Alliance) characters that have killed you, it puts them on a list. I think its suppose to let you know when you are in the vicinity of someone on that list so you can kill them. I only got it recently (after being ganked by at stupid level 80 DK when I was minding my own business). But I think if you are on a PvP server an addon like this is a must. If anybody out there has a kill-on-sight mod that they love, please do share.
Is there anything I'm missing? I'm sure there is a uber mod that I should have and I don't at this point. I'm open to suggestions. I'm also wondering if there are any good mods spedifically for Death Knights (I've been Playing Elliahna a lot these days). Let me know what mods you like and what they are good for.