if it has 0 legs or more than 4 and/or flies, its dead in my house.
I wage complete annihilation of bugs. pest control guy comes every quarter :3 and I keep a can of raid in stock for wasps and other crap that comes around the house
I give things a a fighting chance.
I have a "Horrible Rape Radius" (a term I picked up from WoW, I think).
Basically, if it's a spider or centipede and it ventures within my armspan -- or it doesn't move by the time I get to it -- it's probably going to die. Otherwise, it's live and let live.
If it's a flying bug, however, I still give it a fighting chance because I don't use Raid or flypaper or anything. If I can't kill it with my hand, a flyswatter, or other improvised implement, it lives to fight a bit longer.