You can make a barstool from a single prim. Just copy what you see in the next few lines and in no time you will be sitting on the stool you made!

Make a simple, good-looking wheel from a single tormented ring.

The traditional way to make a door in SL is to use one prim for the door itself and link a second, very thin prim to it as the root prim. Then you put a rotate-on-click script in the root prim. This is not really necessary and is annoying if you are battling to keep the prim count down in a build.

You can use a single prim to make two stair steps. Using a few of these will halve the prims you need to make a long staircase! All it takes is using the Path Cut settings and some rotation of the cut prim.

A low-prim spiral staircase can be made easily and quickly by twisting a half-cylinder.

Yes, it is possible to make a spiral staircase from a single prim! With a little imaginative texture work, and perhaps some scripting, you can have a high-impact look, too.