Personally, I would choose to save that money. The reason why is you never know - maybe something bad is going to happen and you will need that extra cash. So instead of splurging it on material things, it's better to save it for a rainy day, in my opinion. Investing is not safe, given that you may lose a lot more than you invest.
The correct answer would be Incentive.
Incentive is a thing that motivates or encourages one to do something.
Its usually the M1152 model of hmmwvs