Samson was on the brink of death (I'm sure after the Philistines had some fun with him, they were going to eliminate him). In other words, his case was terminal. He prayed for permission to (among other things) commit suicide. And God granted his request. This is what seperates this case from Saul's. When we're told Saul's story, we read nothing of divine approval of his action (in fact, David rebukes the man who says he euthanized Saul), but here God seemingly approves Samson's request to speed his death by giving him the strength to accomplish the task.Judges 16
28 Then Samson prayed to the LORD, "O Sovereign LORD, remember me. O God, please strengthen me just once more, and let me with one blow get revenge on the Philistines for my two eyes." 29 Then Samson reached toward the two central pillars on which the temple stood. Bracing himself against them, his right hand on the one and his left hand on the other, 30 Samson said, "Let me die with the Philistines!" Then he pushed with all his might, and down came the temple on the rulers and all the people in it. Thus he killed many more when he died than while he lived.
So what? Well, I don't think this case supports an individual taking his/her life in their own hands (or even requesting that another human assist them in such), but it does seem to support the idea of praying for a quicker death in a terminal case. Of course, if the revenge is the focus of the passage (and suicide merely an effect), then perhaps no strong case is being made at all.
What do you think?