What cartridge is desired?
Much as I like Ruger #1's, for light weight I'd also agree going with a Hagn, Dakota 10, or a Soroka.
But for tradition's sake, Low Wall Winchesters are pretty light. Ballard Rifle Co is also selling a Low Wall action, that would be strong enough for modern cartridges.
I've thought about taking one of the current Browning/Winchester Low Walls and having it rebored to .30-30. That's not a full custom project of course, but it's fairly easy and inexpensive.
I've also seen an original thin side High Wall where the action was ground down to all the same width, and it wound up pretty light as well.
