All type logos
Many logos are nothing more than type. But just because a logo is all type doesn't mean it didn't take creativity and skill to put it together. An all-type logo, used with a classic face, often creates a corporate look, a solid, dependable, no-nonsense sort of company. Think of the logotypes for IBM, Macintosh, or Pond's.
If you use nothing but characters, you had better be sure you're using excellent typography; check your letterspacing, linespacing, word spacing, the placement of hyphens or dashes, true apostrophes, etc.
If you plan to use all text as your logo, be very conscious of your type choice (duh). As a general rule, don't use any font that is built into your computer (like the ones shown here). Buy a new one.
Be especially wary of Helvetica (Arial is also Helvetica, it's just called another name). Helvetica was the most popular typeface in the world in the 1960s and '70s, so anything you create with it automatically has a '60s/'70s look. Do you want the same visual identity as thousands of other companies and organizations who still have their Helvetica logos held over from the '70s?
You can see here what an incredible variety there is within the limitations of using one main typeface in the logo.