Knights of the Old Republic comes close, but you could argue that the "Force" is a type of magic.
Fallout does indeed occur after a nuclear war. In the first, you play one of the survivors who lives underground but is sent out into the devastated world to find some equipment that the shelter (called a Vault) needs to survive.
I second that. The sequel is even more awesome than the first one, in my opinion.
UFO: Enemy Unknown, also known as X-COM: UFO Defense, is another old, yet remarkably interesting and well-executed game. It feels a bit more like turn-based strategy than a pure-bred RPG game, mainly because you can sometimes have hundreds of different characters in a single battle; most of which die in a single shot. While your characters have many RPG-esque stats and can be equipped with a large diversity of items, the game also involves elements of base management, plus interception of in-flight alien crafts that attack Earth.
"Stephen Wolfram is the creator of Mathematica and is widely regarded as the most important innovator in scientific and technical computing today." - Stephen Wolfram