Mine is long gone after the server crashes of '00. But it was How do birds do it? in General Questions. I was concerned about the logistics with tail feathers.
First thread: Monkeys and the Complete Works of Shakespeare. Still one of my favorites.
Most successful thread: OK, Sec. Rumsfeld: just what ARE the criteria for a “guerrilla” war?, one of my rare forays into political topics. It got 70 replies and 1,598 views. Incidentally, I started that thread on July 1, 2003…
Least successful thread: Ted Bundy’s old house gets torn down. Got 0 replies.
Favorite thread: Football (soccer) and hooliganism. A fairly short-lived thread, but one that hopefully helped to fight ignorance about the prevalence of hooliganism.
Most embarassing thread: ‘Kangaroo Jack’ was last week’s best-selling DVD. Sure sign of the Apocalypse?. Intended this to be a forum wherein people would savage this movie or at least make fun of it–was shocked to find people responding with serious and quite reasonable points about how it was a decent movie for kids.
I really haven’t started that many threads.
My first thread was also my most embarrassing thread. I put it in the wrong forum, asked if it should be in a different (but equally wrong) forum, and gave it a title that couldn’t have been more vague, which was then changed by a helpful mod. Freakin’ newbie. Hereit is. Yeesh.
My most successful was a poll about going to war with Iraq in IMHO, which I started on March 16th, 2003. Went on to 5 pages. It’s here if you’d like to see it.
I’ve always kind of liked this one (A confession for my 100th post) and this one was fun too (Went to the ER last night. What will it cost?)
First thread Help! Changing Wardrobe. Still a work in progress.
Favourite: Religious Views on Evolution. It was a great learning experience.
Least popular: Anyone playing X2: The Threat?. Zero replies and 11 views; clearly no one was playing the game 
First and favorite. A teaspoonful of black hole. I was only slightly embarassed to discover that it should have been titled “A teaspoonful of neutron star.”
Most successful - What can I buy in Canada but not the US?
Least successful - 2 DSL questions. Only 2 replies and one of them was me. 
Most embarassing - Kirk on Enterprise next season. Is it a joke? - I really should have seen that it was an OBVIOUS FREAKIN’ April Fool’s joke. [Insert smack smilie here]
Oooooh, first thread we created!!!
ARggggh, and here I spent 15 minutes looking for the first one in which I posted!!! 
http://boards.straightdope.com/sdmb/showthread.php?t=146591&highlight=umbrella
But this one was a funny and lighthearted rant, by eve I think. Worth a read, or at least a quick scan.
Now I have to hunt down my first actual thread (I don’t create many, just mainly post in others’)
Gak, my very first “real” thread, one I started, is a boring one (insert sheepish smiley).