For the most part I have wanted to match the calibur for the rifle and the pistol...so....

Fiveseven and PS90

Baby Eagle and HK94

But I start running into trouble when I look to the AR, AUG, AK...sure there are "pistols" but they really arn't pistols. They are stockless short rifles. Not something easily concealable or that you could easily carry on your hip.

Oh, and no one has mentioned shotguns...something like the Saiga should be on everyones list.