One of the contracts, Aegis Gambit requires you to look for 10 goldrushers which can become quite time consuming. Here is a very good location to use, easy to get, easy to kill (because of rampage event), and easy to finish.
Just warm up the mini-gun and start blasting away. Goldrushers will start coming out and soon you will have your contract done in no time.
Note - Depending on how well you do, you might have to do another run or two.