One of the more successful collectible miniatures games, Heroclix was going quite strong, with dozens of expansion sets and more than a thousand figures when Wizkids suddenly plled the plug in late 2008.
There are efforts afoot to resurrect the game line under a different publisher, but what will emerge from that effort, if anything, and how compatible it will be with older stuff is impossible to say. It may or may not be a dead game.
Heroclix is a superhero-themed skirmish level wargame. Each figure generally represents a super being, although there are a few that represent a pair such as Batman and Robin and there are some minor characters that are represented by cardboard tokens. Locally they were called "POGS" because they resembled those toys, but I don't know how widespread that was.
The key feature of the game is the patented dialable plastic base on each figure. As the figure takes hits from damage the dial is "clicked" to show new values which often include new or different superpowers. It's a neat idea and it fits the superhero theme well, although attempts to port it to other genres such as mecha, Halo, horror, fantasy and sports have had mixed success.
Because it's about comic-book style combat between super beings, tactics definitely take second place to interactions between powers and the metagame of selecting figures.
Being a collectible game it also suffers from the generally unsettled rules common to that sort of game and the problem of deep-pocketed players having access to better figures.
All-in-all I don't think there's much to interest wargamers in this line, unless they also have a strong interest in comic books.