Wait, was that some sort of achievement? I hope not, because it'll make me angry.
going into prestige mode (or the next prestige, there are 7-10 of them iirc) resets all your challenges and unlocked equipment/kill-streaks/perks. completing a challenge will unlock a title/emblem. prestige mode doesn't reset your titles. Some of the challenges are a good way to show people some of the crazy things you have done like kill someone with a direct hit from a flash-bang or survived 5 wound & recovery in a row without.
some people might think its all pointless but I enjoy challenging myself to play the game in a way that I am not accustomed to like focusing on a sniper rifle when I really suck/ hate them. It sucks at first and you feel like your not getting anywhere but if you stick with it you get a 16 kill streak and people accuse you of hacking.
the lightweight challenge is to cover 250 miles while running with the lightweight perk equipped. what this challenge doesn't tell you right in it's text description is that when you have lightweight on you don't have any of the other red perks on (stopping power, cold-blooded, danger close, etc.) and also that in order to complete the massive challenge (Marathon only required 100 miles) you would need to take on a role that requires lots of running.
so I worked up getting the tactical knife for the magnum revolver (hate revolvers, their iron sights hate me) so this was another challenge in itself. I learned to use a pistol effectively. then once I had the tactical knife I learned to use it effectively which required lots of
running around. I got very good at it, to the point where people would get pissed at me for being a "marathon knife whore" while I danced in their entrails.
its not about pixilated recognition, though i do tend to equip mostly impressive title. It's not even about being really good at the game. It's about being given a scenario you might not favor and defeating it entirely.
That's why I like this game so much. It's not easy, it's not that hard and it has a system of quantifying your progress.