If you've lost all hope that you will get a Nintendo Switch at launch without pre-ordering, there's still a slight sliver of a chance that you will be able to get one! It's being reported that Target and Best Buy will both be stocking very limited consoles that they have not made available to the crowd that is pre-ordering. This isn't anything unusual and fairly typical for retailers to do, but with only a reported 2 million Nintendo Switch consoles available at launch it was not known if there would be enough consoles to go around for such a thing.
Usually, this is something that pisses off the pre-order crowd as these consoles will not be just given out to them. Those who pre-order can usually opt to buy the console, but will then have to forfeit their pre-order money they've previously put down on the console.
If you happen to live in a small area and didn't pre-order, you still might have a chance! Just roll into your local store on launch day and ask around!