Gunner: He's no longer my favorite class, but definitely close. My strategy with him is to just upgrade the weapon and spend nothing else until I do (maybe a small bit for a jump pad activation). How I follow that up will depend on how the opposing team is playing. All of my money goes to me.
Sniper: This one is definitely my favorite, though only because I'm successful in using him. He's most useful in Ammo Mule arena, where I can set up a base on one side of our bridges. I lay down a trap at the jump pad, a trap at the walkway, and I'm set. An Assassin using a Smoke Bomb jump could reach me, but that's it. I should be able to see her if I'm actually watching the arena instead of aiming down a shot. Sniping other snipers is fun. :)
Assassin: Sorry, I just can't play this class. I can't do it effectively. Don't ever ask me to be an Assassin unless the rest of the team is REALLY solid.
Support: Support is only as good as the rest of his team. I'm no good separated from the team. It'll take more education on how each specific map works to play this effectively.
Tank: I didn't play this much. I was successful when I did, but this really isn't my style.
Assault: I need to pick this guy up more. Assault is the fastest character with a gun, and I now see how this can be a beautiful asset.