My first time encountering a Juggernaut in Marathon 1. I loved them all, but I've got a soft spot for the first one. And for all of Infinity's improvements, I still prefer Durandal. The writing and storytelling in the series was (and really, still is, with probably only a few exceptions) second to none. Have you been here: http://marathon.bungie.org/story/ If you scroll down the left side you'll get to tour the levels of each game in the series.