Walnuts, apple butter, berries, bananas. But it's gotta be steel cut oats. Instant is just mush.
+1 I love Red Mill Steel Cut Oats. It takes a little longer to fix, but when you have time it is definitely worth it. Can't stand the instant stuff. I love to mix a little honey in mine to sweeten it. Blueberries are great in oatmeal. We buy the frozen bags of blueberries from Sam's club, throw them in a bowl and put them in the microwave for about 20-30 seconds just to defrost them a little before mixing them in with hot oatmeal. This is a great way to eat it.