Demolition if Let's Game It Out had a say about it.

Basically, you blow stuff up, get money from blowing stuff up, then get new equipment for blowing stuff up.
That's just campaign mode though.

Sandbox is just blowing stuff up to your heart's content, you have infinite ammo, (not infinite health though, be cautious,) and you can blow stuff up for as long as your PC's memory will last.

Did I mention there are mods?

Demolition if Let's Game It Out had a say about it. Basically, you blow stuff up, get money from blowing stuff up, then get new equipment for blowing stuff up. That's just campaign mode though. Sandbox is just blowing stuff up to your heart's content, you have infinite ammo, (not infinite health though, be cautious,) and you can blow stuff up for as long as your PC's memory will last. Did I mention there are mods?