The two characters I got sketched by Brent were from Astro City, and both from stories that I got letters published (back before the advent of the message board). Jack-In-The-Box is the clown-themed hero whose acrobatics and gadgets (including catapult limbs and shock rubber noses) make him a grade-A crimefighter. Jack first appeared in the third issue of the third volume, where a low-level criminal tumbled to his secret identity. In issues #11-12, Jack faced nightmarish versions of his children, and he wound up passing the mantle in order for his unborn son to have a normal life. Here's what I acquired in 2003:
On the other side of the hero/villain spectrum is the Junkman. Hiram Potterstone was a man who turned criminal after he was forcibly retired from his job, relying on his unique inventions for his scores. In Astro City #10 (second volume), he pulled off the perfect heist and retired in luxery, only to find that people not knowing of his deed was unacceptable. He wound up getting caught pulling a similar crime by Jack-In-The-Box, but he was certain to slip away and plot anew. This comes from 2009.
HONORABLE MENTIONS: Carlos Abdulio (first page of my eighth sketchbook), Daniel Acuña (first page of my second book), Franco Aureliani (five sketches, including this nice Dex-Starr/G'nort piece)