The fifth comic: #827 Death Note
Death Note is good, really good. Possibly the best comic I've read so far. It had me not want to leave the train when I got to the end because I wanted to read a bit more. The story is engaging, building up a mystery - not as to the actual culprit, but how the plans of the protagonists work out, what they do and how they solve things. You're given just enough insight into their plans to know what's going on, without necessarily giving anything away.
The ending is unavoidable, but the journey matters far more - how does a kid get to this point, why, and how does he fall in the end.
I just wish it hadn't ended quite this early.