If you could create a painless, inexpensive cure for a single ailment, what would you cure and why?

Common cold. Seriously. Here’s why:

• No cure exists, and an instant cure for it would be really helpful.
• While there are more dreadful diseases like cancer and AIDS which needs treating, well, most of the best minds are already on it, and many answering this question would respond with the same. So enough people already on it.
• It sucks. Royally.