Yes. For instance, someone who is given an impossible choice, during war may commit suicide to show his disagreement. Rationality is sometime cultural, which is difficult to accept to rational minds, including me. For instance, in old China, if someone did something very bad against you, the "rational" way to get revenge was to commit suicide in front of the door of this someone. It would bring an awfull lot of shit on his head, more than what you could do by staying alive...
Even this is very arguable, there are plenty of perfectly rational reasons for suicide.