Sins? I don't want to keep you up all night, so here are some highlights.

Fucking with clients and employers who fuck with me first, or waste my time.

Occasionally not documenting my code (I'm actually pretty good about this), then bitching about poorly documented code.

Honestly wishing other people in the office would *actually* explode, or die engulfed in flames.

Working drunk and/or stoned.

Getting pissed off when I have to do something in a stupid way, or use a workflow that I don't like.

Seriously fucking up out of either arrogance or stupidity, then blaming it on something else.

Zoning out, skipping work, or sleeping in and billing for it (see sin #1).

But my greatest sin? That honor's got to go to becoming a developer in the first place.

I wasn't always a professional asshole, but I fucking am now.