A troll who posts to the comment pages on slashdot. Slashdot trolls have a long and distinguished history, occasionally insightful, often annoying, never boring, the slashdot troll is often more entertaining than the thread (s)he posts to.
A brief history of trolling on slashdot:

1: First Post!!! - As soon as slashdot started the comments system, getting the first comment in became an obsession for many posters.

2: The Golden Age - since before slashdot had a user/login system, The Glorious Meept ruled the trolls, all his posts were easily identified, because they ended with the word "MEEPT!". He was usually coherent, and sometimes even made a good point.

3: Anonymous Coward - After the user/login system, those wishing to troll posted anonymously. The Glorious Meept was still a prolific poster.

4: Voting - In response to the falling signal/noise ratio Hemos and Cmdr Taco implemented the moderation system. 400 of the eldest and wisest slashdotters were given the power to raise and lower a comment's score. Posts by logged-in users started at a score of 1, and Anonymous Coward posts started at 0

5: Karma Whore! - Trolls and regular users alike felt oppressed by the moderating elite, thus Cmdr Taco instituted Karma and meta-moderation and started selecting moderators randomly from a pool of regular users. Meept stopped posting somewhere in this period.

6: Natalie Portman, Grits, and Beowulf: Segfault closed its comments section after much abuse from trolls. The displaced trolls moved to slashdot, raving about hot grits, Natalie Portman, naked and petrified, and stirring up dissent against the moderation system, which they claimed was censorship.

7: sellouts: The current trolling is mostly about Cmdr Taco et al selling out, when VA Research bought Andover.net. They alternate between mocking Hemos for making money off of slashdot and slamming Cmdr Taco for losing money on the Linux IPO hype, depending on how VA stock is doing that day.

Hemos, or any old-school slashdot users, feel free to correct me if I mixed up any chronology here.
update 4/17/01
Millennium: Yes, I left some out, the hiding of nasty porn links in innocoupus looking titles hadn't really gotten started when I noded this. There are also crapflooders now, who just post random garbage, or worse, ASCII art pictures of the goatse.cx guy. You're old-schooler than me, BTW, my slashdot ID is about 9000.