You find the creators of the game on the final challenge, Meet your Maker(s?). You have to fight the SFH versions of Mike and Justin, who are amazingly powerful, and kill them 15 times. The difficulty rating is impossible.
For classes, I recommend using the assassin your first time through with snipers, (nothing else) as it allows you to complete the campaign the easiest, giving you fighting experience for harder playthroughs such as the medic.
If you have the patience, the Tank can really pay off in the end, but it's not a very good class at first and you'll spend a lot more time repeating missions and doing quick match.
I've never played as the medic much, because personally, I hate the class. SO you'll need to get tips from someone else.
The commando is one of my personal favorites, but it's very important you keep your weapons up to date. If you go up a difficulty, a new gun is a must if you use machine guns. Explosives require a little training at first, as you need to get pretty accurate and need good timing. You'd think it would be easy if you played as the assassin before, but since the rocket travels much slower, you need to target it so it is difficult to dodge. Once you get a heat-seeking rocket this shouldn't be a problem.
That's all I got right now. Also, I'm stuck on challenge level Norris, Chuck. IS anyone else knife range unevenly proportioned?I can only seem to hit the enemies from about double the distance of the knife itself, and no closer. :/ My friend said he didn't have a problem with it, and tried to convince me it was because he was used to long-range melee weapons. Then I reminded him he doesn't use melee weapons, so I'm sure it's a glitch with certain computers.