1) do you think suicide can ever be a rational decision? if so under what circumstances?
1) Greek Stoics, whose philosophical set extended to the Romans later on. Stoics would be known to commit suicide as a form of political protest when liberties have been stripped to such a point (perhaps in times of war, etc) that one becomes a slave or some related level of society. You cant oppress anyone thats not alive, now can you? It is said that the Roman senator Cato ripped out his own bowels in a stoical suicide, in order to protest Julius Caesar's claim as Emperor. Caesar would have most certainly pardoned the Senator, however, Cato avoided this as it would have acknowledged Julius Caesar as Emperor (thus, a stoical suicide).
Oddly enough, this exact practice was exhibited on the other side of the world as im sure youve heard of Japanese
Seppuku (has also been used to protest the actions of a fuedal lord or emperor).
2) Tyrannical world leaders whose population revolts and breaks out in military coup have often found death by their own choosing to be a better option than facing the wrath of the mob (which would probably include flaying, impalement, crucifixion, perhaps just a light beheading, etc).
3) Spies caught by the enemy (death instantly by cyanide and a bullet, or death after many weeks of arduous torture?).
4) Warfare, especially when your enemy is the imperialistic type planning on using your carcasses as an example to neighboring city states / provinces. Manny occurrences throughout history have included civil militias decapitating their wives and children, and then falling on their own swords, in order to avoid being flayed / impaled / crucified to intimidate nearby towns.