I'm particularly fond of Shakesperian insults. Here's a link to an old thread:
http://wordsmith.org/board/showflat.pl?Cat=&Board=wordplay&Number=4262

In the same thread is tsuwm's abecedarian insult:
"Sir, you are an apogenous, bovaristic, coprolalial, dasypygal, excerebrose, facinorous, gnathonic, hircine, ithyphallic, jumentous, kyphotic, labrose, mephitic, napiform, oligophrenial, papuliferous, quisquilian, rebarbative, saponaceous, thersitical, unguinous, ventripotent, wlatsome, xyloocephalous, yirning, zoophyte!"