Seriously, skipping breakfast (even waiting too long to eat it) will wreak havoc on your fitness goals and energy levels - not to mention making you crabby towards all you meet.
My vote? Make sure it contains at least one serving of protein and at least one serving of a fruit or vegetable. Here's one of my favorite choices: Erin Baker's Double Chocolate Chunk granola with almonds and fresh strawberries in milk. YUM.