Suicide is often a fairly impulsive thing, and suicidal people can be deterred by even slight inconveniences. That's why things like suicide barriers on bridges work. Guns are a very attractive method of suicide—they're rather instant, painless, easy to use, and so forth. I'm in favor of gun ownership, but suicidal people, deprived of easy methods of suicide, will often reconsider entirely. The moment will pass and they will not kill themselves.
Of course, some people decide to kill themselves and remain very determined about the process. Not all suicides are alike.
After that we can get rid of rope, fire, plastic bags, anything with a sharp edge, carbon monoxide, carbon dioxide, anything flammable and water; just to be safe.
I think your point is that guns make suicide easy, and I get that; but I think it's a tough spot to defend in terms of gun control. Suicide is easy, people will always find a way to do it.
If you've got a cite that shows that the presence of a gun increases the chance of suicide, I'd like to see it.
Of course, correlation != causation.
Lots of suicidal people buy guns. When they can't get guns, they use other methods.
Japan's suicide rate is twice the US's, despite Japan's strict gun control.
http://en.wikipedia.org/wiki/Suicide_in_Japan#Methods
Common methods of suicide [ in Japan ] are jumping in front of trains, leaping off high places, hanging, or overdosing on medication.
A newer method, gaining in popularity partly to publicity from Internet suicide websites, is to use household products to make the poisonous gas hydrogen sulfide.