Jesus didn't kill Himself. He laid His life down, into the hands of His enemies. Samson didn't personally inflict fatal injury to himself. What he did was destroy the pillars of the temple. He didn't want to end his life because he had overwhelming problems and didn't trust in God. Samson's motive was destroying the wicked enemies of God and of Israel, for the benefit of Israel (as a result the Philistines weren't a problem for Israel for a time). If the collapse of the temple did not kill Samson, he would have went on living in faith and joy in the Lord, not depressed or overburdened with mental/spiritual problems. Samson acted upon faith in God. Jesus Christ did not inflict personal injury either; He laid His life down and His enemies murdered him. You cannot equate these examples with suicide today. The motive behind suicide today is neither of the above. People kill themselves today because of their overwhelming problems they can't deal with, and because they don't trust in God, and don't live in submission to Him.

Exodus 20:13 both the letter and spirit of the law, forbids suicide.