So, what are the absolute best exercises for abs/stomach?

Mine are probably my most underdeveloped muscle, and even though I got 20 more pounds to lose with how little abdominal muscle I have, I'll still probably have a gut.

Any tips in general appreciated, getting some Optimal Nutrition Whey from Costco and joining the gym next week.

This is a semi new pic, Ive lost 5 pounds since but it's hardly noticeable.