Marline spike

A fat bodkin with an ogival taper to its point, used for opening the
strands of wire or rope cable when splicing. Some people use the pointed end to
turn shackle pins, but the curved taper is not appropriate to that application
and the spike is likely to slip out of the pin and into your flesh. A
shackle-key is better, and some good hands prefer a pair of pliers. (See also