Growing up, I was partial to the Armor Wars storyline in Iron Man. Tony loses Stark Industries to Obadiah Stane, and discovers that many of the other tech-using characters in the Marvel Universe are using versions of his technology. Tony sets up a new company, and decides to track down every one of those characters and take his technology back. It was interesting to see a super hero take initiative on something instead of just waiting for a villain to show up. I can't recall which villain, but one of them hears about what Iron Man is up to and just gives his gear up to avoid a fight. Tony invents a stealth version of the Iron Man suit to fly to Russia and take down Crimson Dynamo and Titanium Man. Stark's actions also put him at odds with the government, and at one point Tony narrowly escapes a confrontation with Captain America.This all culminated into a final fight with Stane (in the Iron Monger suit), and Tony (in the prototype red & silver armor), and Tony reclaiming Stark Enterprises.