Other people add things to their porridge that I haven't even HEARD of!
Agave nectar- sweet taste, like liquid honey but without the strong honey flavour.
Lucuma powder- Lucuma is an exotic Peruvian fruit. You can use it as a sweetner or a flavour. It tastes kind of like vanilla, and is better in hot foods than cold as it is quite chalky.
Cocoa nibs- part of the cocoa bean. Crunchy. Taste like chocolate but not sweet (but not bitter like cocoa). Use them as a garnish or in place of choc chips.
Pandan- If you try just one thing on this list, try this. It tastes like sweet pastry, no, lemon honey, no, flowers... anyway it's sweet and aromatic and delicate, in the same way Earl Grey tea is, buit with different flavours of course. You can get them fresh, frozen, dried, paste or as an extract. Kewra is an extract that's distilled from pandanus flowers which is also popular apparently. I tried some pandan essence in a can, it had a light fresh taste, like water, or grass. But to really taste it you need the extract.
Dried Longan- think chopped up date, but from a different fruit. Longans are just like lychees and rambutans, to give you an idea.
Goji berries- taste like sofa, but they are good for you and they do grow on you.
Medjool dates: Big, fat dates. Very sweet, with not a strong date flavour.
Lingonberries- a bit like cranberries. I've only had them as jam, but they're nice.
Huckleberries: I've always wanted to try these! Apparently they're like blueberries.
Maca powder- an interesting one. The taste starts off as asparagus, but then warms into strawberry jam, following into notes of woodsmoke (a sort of lapsang souchong). It's not unpleasant, but takes a bit of getting used to.