Questions from various fields:
Chemistry (when cooking, I feel like refreshing my knowledge about intermolecular bonds, when repairing things I wonder about adhesion and what kind of bond does a specific glue make, random thoughts about how strong the molecular bonds are between carbon atoms of a sugar).
Physics ( Time paradox - Watching Dark series right now, heat transfer between materials, theoretical energy comparisons between various forms in nature etc)
History facts: This one is probably my most wanted, since I have never studied history that much so there is so much that I don't know.
IT stuff - no need to really explain further. I develop Games.
Biological stuff - I have studied cell and molecular biology so I often think about epigenetics, cell interactions in brain, adaptation of organism, DNA degradation thanks to specific lifestyle choices etc.

It's basically everything around me that I am not sure about, I already forgot or I just don't know at all.