I’m going with mhendo andJodi. Smart, thoughtful, funny, articulate. To me, they exemplify the best of the SDMB.
If no one’s responded to this thread in a coupla hours, I’ll post more random personal favorites.
Jomo Mojo – as a duffer in the field, I respect the hell out of his linguistic knowledge.
China Guy – happy to lend insight into Chinese culture, and does so without a hint of condescension.
Candid Gamera - I love the user name and I remember some funny posts by him.
fishbicycle - for starting a thread on puns!
I am a just a pun-ho. 
Just two? Okay.
In no particular order:
Baker, because she likes to play in my “Finish the…” story threads.
Biblio, because she has wonderful taste in tv shows.
There are more, trust me.
Qadgop the Mercotan – gotta love a guy that can answer serious LOTR questions off the top of his head.
Lieu – every day I see four or five posts that I wish I had made.
**Jurph ** - for his patience-of-a-saint handling of BoyScout11 in GD last week.
**Otto ** - for our mutual love of all things ALIAS.
Chronos - For covering justa bout every corner of physics, and doing it in a way that’s easy for the lay reader to understand.
AHunter3, who’s gone out of his way to help me with a little computer thing I’ve got going on.
Tamerlane, for his polite and generous erudition;
Polycarp, for his plain, utter decency.
RumMunkey. Witty, insightful, and kinda sexy!
A couple MPSIMS favorites -
Rue De Day - Because of the MMP, natch.
swampbear - Because of his oft-mentioned love of burly men.
Susan
I’d have to say Diogenes the Cynic. One for having such a cool name I wish I had thought of it first. Two, for answering all kinds of questions and backing them up with cites. Sure, people say he’s abrasive sometime but I think he tries to answer a lot of things fairly.
And I’d have to say **flamingbananas ** for my second. Flamingbananas, I am a straight female so don’t get me wrong when I say I think you’re really cute. I still remember your “I’m going bananas” thread about how you tried to eat a wrapper and throw the candy away, I think.
ivylass, because she has wonderful taste in TV shows.
and,
Eve, because she always makes me laugh with her witty one-liners.
There are probably others, but I thought of these two straight away:
SentientMeat - Even though I’ve never posted to one, I’ve immensely enjoyed his Political Compass series of threads in GD. I’ve also noticed that other posts he makes tend to be well thought-out, articulate, and polite. One post that springs to mind is in this thread. Although it is arguable whether the OP deserved a reply, SentientMeat was the only person to attempt to answer the question. Also, his political views are very similar to my own, which is a bonus.
QED - Possibly one of the biggest enemies ignorance has ever faced (apart from Cecil, of course).
BrainGlutton starts really interesting threads.
elucidator writes very witty posts.
elucidator, even though we are not of the same political cloth, I find his posts to be delectibly comical and insightfully humorous. And sometimes even true.
NoClueBoy, for his on-the-spotness.
Just two? But… but… but ther’s dozens!
Jodi is smart as a whip and remarkably well reasoned. I dig her chili.
CrankyAsAnOldMan is simply just good people. She’s my fantasy godmother.
ivylass:
lieu:
Well, heck, once you’ve named two, come back and name two more! 
Like I’m doing:
monstro – Because she (Lord, I hope I’ve got this gender thing down) always says things in a way that a) makes me wish I’d said them, or b) makes me see something in a new light.
erislover – A passionate and incisive defender of his views, whose intellectual curiosity leads him constantly to reassess his take on the world. (Anyone who remembers erl’s previous incarnation can attest to that last!)
I like the fact that most people haven’t repeated someone that someone else has named (because you just know we all have tons of posters here that we love to death), but in honor of elucidator, who’s been named a couple of times so far, I have to give props for the funniest thing I’ve read in a while. luci wrote it in a GD thread, and it tickled me so much I repeated it (with attribution, natch) to my girlfriend that night:
That cracks my shit up.
Liberal - Stirs up shit but generally has intelligent posts.
Diogenes The Cynic - See Liberal.
I like their style. What can I say. I can’t post like that cuz I’m too nice a guy…a trait that I can’t seem to get rid of.
World eater
and
Weirddave
Polycarp - who can be counted upon to show up and bring order to chaos.
**lieu ** - cuz you can never have too many poop stories! 
There are dozens more. I always read the posts of some, just because they can be counted upon to lucidly present ideas I disagree with.