Surly whether someone feels sucidal has little to do with being a Christian or not. Anyone can have such feelings at any time. Its how a person reacts to them.
Satan uses suicide to tempt people into thinking they have a choice whether they live or die - but only God has that authority.
The modern world has become so saturated with depression and suicide that they are almost commonplace. Christians are as vulnerable to these as anyone, perhaps more so because satan is out to rob them of peace and joy and will try anything to destroy lives.
Christian who feels suicidal needs to be loved, to be brought into fellowship and to be prayed for and with and should never be made to feel that what they are going through is wrong because they are a Christian.
Obviously, I am not condoning the act of suicide in any way, but suicidal feelings in any individual should be addressed and counselled the individual should never be condemned or judged by Christians. Afterall - 'there is no condemnation for those who are in Christ.'
Even those of us who are not feeling suicidal can be guilty of wasting the life God has given - ever said, 'I have some time to kill,' or, 'Iwas just killing time'? We should not be frittering away any priviledge that God has afforded us - Christ came so that we could have 'life and life abundant' and, as Christians, that is what we should be claiming and utilizing.
Redeem the time God has given you, so that you'll have plenty to tell him about when he asks you what you did with it!