Missons the Army can currently complete. The Marine Corps, in some ways redundant, with respect to missions (but we have a different tread for that).
The Marine Corps has the same issues with HUGE waste.
It's not something that resides only in the Marine Corps though. The entire DoD gobbles up FAR too much money. Now that would be a scary audit.
But we draw lines. If you thing there needs to be cuts to DoD, you're not patriotic. I'm conservative. There is far too much spending in the U.S. Not only entitlements, but DoD, DHS... some departments do more with less, and others just waste. Will it be painful, not only for the budget shops but also the personel? Absolutely. But it needs to happen.
As for comparing Marine Corps v. Coast Guard missions, I usually see that argument from people who know very little about the Coast Guard missions.