Great topic Nero.  I've learned a lot about the folks who responded.  Kristi, thanks for the great definition.  beth06, I greatly appreciate your thoughts as well.
I think so often, because of some mishandling scripture etc., that the word sin, and the depth of what it really is, has been greatly misunderstood.  From a christian perspective, "all have sinned and fall short of the glory of God."  In that respect, we are all the same... the playing field is level.  If one is a believer, the penalty of sin (hell/separation from God) has been taken on by Jesus - he, being sinless, met the debt of missing the mark perfectly. 
To get to the point of seriously attempting suicide one has to be in a terribly desperate place.  In my life, I've come close a few times.  As a teenager, I slit one wrist before "snapping out of it".  In my 20s I tried to overdose on speed - could actually see my heart beating through my chest (that was pretty crazy) before I passed out.  Sometimes, because of the lifestyle I used to lead, I am amazed I'm still alive.  Right now I've got all kinds of health issues - have been in and out of the hospital 3 times since October.  What is funny is the peace I've had in the midst of it all - especially in contrast to all the turmoil of my youth.
Is suicide a sin...? yes, as are so many things we do and choose.  Is it the "unpardonable" sin? no.
Thoughtfully... LGF