I'm a Fiber One freak, too. It's a tiny bit cinnamon-y and a tiny bit sweet with a good crunch.
My "treat" cereals are Weight Watchers Vanilla Puffed Wheat (it has Splenda and berry flavor too...I have to buy this sparingly as I *will* eat the whole box if no one is watching!

) and a cereal made by Erewhon: Crisped Brown Rice (basically Rice Krispies made from brown rice without the sugar). You'd be surprised how good plain shredded wheat can be...and you can also have Cheerios (plain only). I add dried fruit (no sugar) to my cereal...dried Goji berries are my favorite, but I use all sorts of tiny pieces of dried fruit or fresh fruit, like berries or a medium banana. That really makes the cereal taste good!
However, I second
Schmoodle. While Oatmeal, made with milk, has enough protein to get me through the day if I eat it for breakfast, plain cereal and milk doesn't. I eat it for a snack. It has enough complex carbs (in the cereal and the milk) and protein to make a great "pick-me-up!"

I stick with heavier concentrations of protein and veggies for breakfast.