I'm not a comic-reader at all, but I recently found out that Colossus gained the Cytorak's powers turning into the Colossonaut (Unstoppable Colossus); I'm ready to start. Can anyone tell me which issues feature Colossonaut or where he is has a significant role? I am specifically interested in any issues where he is wrecking people (Thing, Red Hulk etc.)

Try Uncanny X-men Volume 2, the whole run (it's only 20 issues) or Uncanny X-men Volume 1 from issue 542 through 544. He also had it through the whole AvX event where you'll find most of his one on one throw downs with the Thing and Red Hulk.

Thank You! You just saved me a ton of time trying to figure this stuff out via google searches.