Shot gun, specifically something easy to maintain and use. Remington 870, Mossberg 500 are you main go to choices. Proven, reliable, used by the military so you know they are tough. Personally I would get a mossberg , use buck shot. If you have an intruder you shoot to KILL, not wound. A wounded guy will come back with friends with the intent to kill you, or he will sue you blind. I don't know if Oregon has a castle doctrine, if it does you are good to go.
Mossberg makes some great shotguns, you will probably want a rail on yours for a tactical light attachment. something like the rolling thunder or a thunder ranch are good ones...
rolling thunder
a cruiser is very portable and fairly easy to conceal.
Is there a better shotgun? Sure, winchester model 12 and model 97 are both better, especially in trench gun configuration. but they haven't made them for 50 plus years and they cost too much, but they are the best pumps ever made. Most will have been shot millions of times before the first failure.
Model 1897 trench
Model 1912 riot
The 1897 and 1912 have no trigger disconnector, if you hold down the trigger they will fire with every pump. You can get all 6 shots off in under 1 second if you are quick. Starting price for a 97 trench that is in really good shape? $3,000-$4,000
You can get a plain Jane field model from Mossberg in 12 gauge for $300, same with the Remington 870 express.