Comic universes no longer active, Bravura, Continuity, CrossGen, Future, Malibu, Ultraverse... and others that are 'no longer with us' today (or only recently brought back).
I've read maybe five or so issues of it, and would absolutely pick up a run at the right price. Recently there have been TPB's of it, but I'm not sure how much of the series they cover.
this is technically not a dead comic because IDW recently published a new Grimjack mini-series by Ostrander and Truman, and they are reprinting all of the originals in new TPBs.
I've read some and I think they're pretty cool genre stuff. if you like sci-fi bounty hunter stories give it a try.