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The hints were: "Team Fortress" and "classic" in the text, last prize, and the game is also visible in my Steam profile. Then those who never played the game could find (with some luck) the page Weapons_(Classic) and (maybe) spot a bright green thing on it.
Short conc jumps video with acceptable quality.
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Solution: find the transparent tip at the bottom, TF2 class #3 is Engineer, the page Engineer (Classic) says:
Your Dispenser will damage enemies upon detonation according to how much ammo it has stored. You can use this as an improvised bomb.
And here is kind of related 19-sec TF2 video ;-)
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Solution: after removing "555-" part we have the number 129211. First three paragraphs end with quote by Oprimus Prime and all prizes have levels as prime numbers.
Trying to see if 129211 is prime, we get 129211 = 157 × 823 where both factors actually being prime numbers. Bing is nice here.
Then the difference between the two is 823 - 157 = 666 which kind of matches the format made out of 3 emoticons.
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It allows Heavy to run 35% faster for 15 seconds. The German guy reference is googlable to Ludwig_(surname).
The names of TF2 characters are revealed through official comics and you can find them in "Bio" section in wiki.