First of all, you cannot compare to the slightest degree the issue of suicide today, and the events that occured in the Old Testament concerning Samson and his death. Samson was not depressed, he did not reject God or rely upon his own efforts to survive, he did not hate life, and he did not seek to resist the will of God. Samson, like Jesus, "laid his life down for his friends," that is, the nation of Israel which he ruled over as a judge. His actions, which led to his own death, were justified, they were the result of prayer and faith in God, and they were done in the best interest of God's people, and for the vengeance of God's wicked enemies. This cannot be said of and likened to the cases of suicide today. People commit suicide today, because of spiritual, emotional, mental, societal, etc, unrest and discomfort; they kill themselves because they are depressed, and hate their lives; they no longer seek God, nor do they trust in His salvation, but instead they take matters into their own hands and live according to their own wills. Murder is not unforgivable of course, as David committed murder and was forgiven; and Paul, before converting to Christianity, consented to the death of many Christians. However, the act of killing yourself is not the issue. The issue is that continuous, unrepentant lifestyle of rejection of God, which leads the person to kill themselves. An unrepentant lifestyle is unforgivable. For Jesus declared "Unless you repent, you will all likewise perish," (Luke 13:3). And Hebrews 10:26-27 declares "if we sin willfully after we have received the knowledge of the truth, there no longer remains a sacrifice for sins, but a certain fearful expectation of judgment and fiery indignation..."