Well, ever since I discovered that both milk and conventional cereal are really expensive, and that for the price of one box of mini-wheats, I can get kilograms of oatmeal, I’ve been eating plain oatmeal every day. The recipe says to add salt, but salt isn’t cheap, or good for you in large quantities.
Oatmeal. My favourite cereal, from an economy standpoint.
I partial to Cherrios and Honey Nut Clusters. And maybe Crispix.
I’m reminded of my sole criterion for selecting a cereal as a child in the 70’s: – the “free inside” giveaway.
My fav – Honeycomb’s license plates. I presume there were all 50 States’ license plates distributed, but we never even got close to getting all 50. As a result, though, I cannot eat Honeycomb at all anymore – it was the only cereal I ate for a long, long time…
Another non-sweetie: grape nuts, plain or with sliced bananas, or oatmeal made with milk, not water. Or Uncle Sam’s high-fiber cereal. Or grits with olive oyl, bran, salt & pepper. Oh, yes, skim milk with any of them & no extra sugar. ALso cheerios in a pinch, but in any case it’s usually the house brand.
Maybe I’ll try the ice cream with chocolate frosted sugar bombs, if I can find 'em. 
It has to be Count Chocula. It just gotsta be!
Isn’t it terrible? Cereal is a consuming passion of mine. After reading this thread yesterday, I went home and had two giant bowls of corn flakes for supper.
I LOVE IT! I discovered it while I was pregnant when, believe you me, you need all the fiber you can get. For extra power, top with prunes. No, I’m not kidding. 
I’ll have to agree with Coca Pebbles, and on occasion Fruity Pebbles. And last night I had Peanut Butter Crunch for dessert.
My favorite though is Count Chocula BUT current versions pale in comparison of the versions of my youth. You know, when Count Chocula was a 2:1 ratio of little BB marshmellows to cereal. Each spoon full was packed with 'em. Now, yes the marshmellows are bigger, but there’s hardly any in there. sigh
GES
The Special K Red Berry stuff is my absolute favorite. With the exception of chocolate ones though, there aren’t many cereals I don’t like.