Household & Garden
Even if I don't count it as one of my/our hobbies, there are always countless small projects in the household and garden that can be enriched and solved with a 3D printing solution.
A hose adapter here, a matching spice rack there, replacement hooks for the bathroom, a spoon holder there, special flower vases for this, flower pots for the wall, cup holders for the garden chair, book stands with a charging station for the phone, cookie cutters, bottle holders, etc.
There are actually no limits - apart from your own inventiveness - for solutions and applications...