The Ninja can fire while cloaked without revealing itself. Because of its Propulsion bonus, it can easily get an amazing amount of cloak time, allowing it to take out nearly anything without being attacked. Believe me, the Ninja is actually very valuable, especially later in the game when you need to take out or Virus a strong enemy. I'm not sure if its better than the Sniper (which has its own benefits), but I would take it over the Brawler.
I love explosives. Except for/especially when I miss an explosive rune when firing a Plama Cannon.