Titanium marlin spikes are useful for tying / untying certain knots, rope splicing, or sewing. I have some customers who use these as tent stakes. Available in 4" and 6" lengths. 

Dimensions:

                     4" long, 3/16" diameter, 1/8" hole near base. Weight: 11g.

                     6" long, 3/16" diameter, 1/8" hole near base. Weight: 17g.