Copper tubing, in small diameters is fine, see page 25. http://www.copper.org/publications/p...e_handbook.pdf
I would doubt the corrugated stuff without data. Also, consider the annealed numbers if you need to re-anneal any bad bends.
Don't use an unknown "type" (K,L,M).
I've thought about 1/8" ACR for steam punk stuff.
Fittings for such things can be the bigger problem.