You have many options: the 2 questions are: how big are the holes, and what is its end purpose??

Soft-Flex - Nylon coated braided steel, crimp to finish available in .010, .014. .019 and .024. For a real heavy piece you can double this, then crimp to finish. Recommended using the proper crimping tool. Other brands such as Acculon and Tigertail tend to be more wire-ry.

S-Lon: similar to CLon, available in Micro, Fine, Regular, and Heavy, great for knotting, micro-macrame and braiding. Much stronger than silk, should be pre stretched.

Tuff-Cord - a nylon thread similar to S-Lon - 6 thickness, and many colors.

Chinese knotting cord: Avaialbe in .5mm, .8mm, 1.2mm and 2mm - many colors and pretty.

Ultra Micro Fiber Suede Lace - a smilier look to suede leather - many colors and knots well. This can also be braided.

Waxed Cotton cord available in .5mm, .8mm, 1mm and 2mm, Limited colors, and much stranger than leather options. The wax feeling varies among brands. More cords are either bonded or waxed.

Hemp - typically in 10lb or 20lb, many color choices. The first pair of Levi's were made from Hemp!! a little course - but nicer than Jute.

Fireline® is a pre waxed, braided cord consisting of gel-spun polyetholine –Available in 4lb, 6lb, 10lb and 10lb. - much stronger than fishing line which is made to break down with UV.

http://www.globalbeads.com/shop/category/stringing-material/

I put together an Infographic to help our customers.