Instead of pulling the trigger—or slashing yourself and leaving a bloody bathroom, or drowning yourself and leaving a gross, bloated corpse—try one of these cleaner, safer (for those around you), even environmentally friendly options for offing yourself. Mind you, we're not advocating suicide. But if you must: Here are several options, from worst to best.
Hanging, while relatively neat and self-contained, is not a quick-and-easy thing. Unless you break your neck (unlikely), you'll slowly suffocate. Starvation and dehydration are also less-than-optimal methods. While ranking high in environmental friendliness (you're saving resources!), it's slow. And there's always a risk of a Shiavo-style intervention.
Carbon monoxide poisoning leaves a pretty corpse. Unfortunately, while simple sounding—start up the old emission-spewing auto in the garage, close the door, and wait—this method is actually ineffective (and also bad for the ozone). Catalytic converters have reduced the amount of CO in car exhaust, so it may not even work. The more effective solution, firing up a charcoal grill in an enclosed space, carries fire hazard risks for your neighbor, can leave soot stains on the ceiling, and the fumes could knock out the person unlucky enough to find your body.
Instead, try asphyxia with a plastic bag. You're recycling, you'll contain any byproducts of suffocation (like vomit, especially if you combine this method with an overdose), and you won't hurt anyone else.
Nine grams of pentobarbital would be swell, if you can get your hands on it (it's what Oregon docs prescribe for assisted suicides). If it's good enough for medical professionals, it's good enough for us. But unless you're apt at faking a terminal illness, you're out of luck.
Which leaves death by exposure, an A+ method of ending it all. Portlanders are fortunate to live within spitting distance of Mount Hood and Mount Rainier, two places that meet your hypothermia needs practically year-round. For best results, wear a thin layer (or get naked), and get above the timberline. Take public transportation (more enviro points!), so rangers don't find your abandoned car and launch a search. It might take a day or two (unless you're wet), but it's a painless way to go.