Earlier this year I built up a light weight 29"* uni based on this thread: 29er rim options?
I used a Velocity Dyad rim, 700x45 Resist Nomad, 32 hole Nimbus ISIS hub, and Qu-ax lightweight 114mm cranks. Even with a cheap steel frame the whole thing weighs around 10lbs.
It’s great for rides around the neighborhood, short trips to the store, etc. You could go narrower on the rim/tire (search for road razor or bacon slicer) but I think the 700x45 tire is a good balance between light weight and still having some cushion; it rides nicely and still feels quick.
*Technically, the diameter of the 700x45 only measures 28.5" so it’s not quite a 29er.