My two things favourites:
The Two Things about Blogging:
1. Everyone who runs one is a kook.
2. Everyone who comments in one is a kook.
The Two Things about World Conquest:
1. Divide and Conquer.
2. Never invade Russia in the winter.
The Two Things about Binary Systems:
The Two Things about Biology:
1. Evolution is the process through which genetic structures that are better equipped to reproduce viable copies will tend to proliferate.
2. Except for the Platypus.