Technically, Thunder's MOS is "Self-Propelled Gun Artilleryman" but that's kind of a mouthful and also kind of silly.
That being said, he has a really nice costume design and I always appreciated his unique headset and visor.
For Thunder, I used the Heroclix Soldier from the Man of Steel set and added his headset with green stuff and pieces of paperclips.
He traded in his monocular for an assault rifle. Good choice!