Single-letter domains

CNN.com: Single-letter domains might earn seven figures

I don't see how anyone would want a single-letter domain for marketing purposes: q.com, x.com, z.com, i.net and q.net doesn't ring a bell, but are currently being used. The only one that rings a bell is x.org, but you wouldn't know that one unless you are a Linux hack.

For more on single-letter domains see this Wikipedia entry.