I would say dips or weighted dips. Close grip bench second. I would have said skull crushers which built most of my tricep but i got too strong in it for my elbow joint. so heavy benching would send sharp pain in my elbow. it put me out of benching, dips, skull crushers or anything invoving the tricep and elbow for about a month and a half. so now i don't do skull crushers as my primary movement. Close grip or Dips. I like to alternate. By that time my tri's are fatigued so i can use lower weight that my elbo wont feel pain from.
Scaggs