While I find all the armor appealing in some capacity, if given a choice there are more than a few I would discard.
Space Marine armor for example is incredibly protective, and is in fact the second most protective personal armor in the WH40K universe. When you consider that even the crummy armor Guardsmen wear is vastly superior to modern infantry armor, that says something. Unfortunately, the armor also weighs in at nearly two tons, and combined with the bulk I'd find that there is absolutely no commonly available transportation that would bear my weight.
The Terran Marine armor seemed to have little that was actually good about it and hardly seemed to be a barrier for the horrors of that universe. After seeing so many of my marines felled in game after game, I'd say I'd ditch that death trap in a heartbeat.
Fear 2's armor is more of a walking tank than armor so I don't really think it counts. If I were to choose something from this category it would almost certainly be a 'mech from the Battletech universe (Original Battlemaster obviously).
Section 8's armor seemed to be nothing more than a derivative of Tribes armor. The joy with Tribes armor is that there are versions that would actually allow me to enter a modern personal vehicle without much effort while still having a huge amount of protection and vastly improved mobility. Tribes armor would therefore be my choice, or, failing that, the armor from Section 8.