Warren Ellis is one of the great comic writers. At this point, I'd arguably put him just under Moore and Gaiman. He's done everything from hard-hitting intense drama stuff to balls-off outrageous comedy, and most of the spots in-between. Nextwave is about the three steps beyond the normal end of that comedy spectrum, but I'd call it the best thing he ever wrote.
Ambush Bug, however, is essentially what Deadpool came out of. He was a DC character who showed up originally as a villain, but over a couple of one shot appearances in Action and DC Presents, he became more and more of a comedic character, culminating in a series of miniseries and specials throughout the 80s and ending in the early 90s. There had been comedic characters (and even characters who broke the fourth wall by addressing the reader directly) before, but the Bug really set the template for what was to come, and he's still my favorite. Everything I've read with Deadpool in it has basically just portrayed him as Ambush Bug with guns.
