Do not choose commando unless you're going to snipe. The knife is a piece of stuff and does random damage between 2 and 9, and cloaking is easily noticed by anyone who's not handicapped. Also, the sniper rifle damage is nerffed greatly at close range.
Pistol + most powerful Sniper (the one with recoil) + Troop Trap (lvl 1 is all that you need) + PowerShot (Lvl 1 is all its worth + Elixir (max it out)