I can describe a few famous lettermark logo designs to give you an idea of what they look like:

1. **IBM**: The IBM logo is a well-known lettermark logo. It features the company’s initials, “IBM,” in a simple and iconic typeface, with horizontal stripes through the letters.

2. **CNN**: CNN’s logo uses the lettermark approach, featuring “CNN” in bold, red letters. It’s a highly recognizable and straightforward design.

3. **NASA**: NASA’s logo is a combination of a lettermark and a wordmark. The iconic “worm” logo features the letters “NASA” in a distinctive, sleek typeface.

4. **HP**: Hewlett-Packard’s logo is a lettermark consisting of the initials “HP” in a blue circle. The design is clean, professional, and easily recognizable.

5. **HBO**: HBO’s lettermark logo features the initials “HBO” with the “O” appearing as an abstract, stylized camera lens. It’s a creative use of the lettermark concept.

6. **LG**: LG’s logo incorporates the letters “L” and “G” in a simple, red and gray design. The “L” appears first, followed by the “G,” creating a balanced and symmetrical look.

7. **AT&T**: AT&T’s logo is a lettermark with the company’s initials “AT&T” enclosed in a blue circle. It’s a classic and timeless design.

8. **BBC**: The British Broadcasting Corporation (BBC) uses a lettermark with the initials “BBC” in white letters on a black background. It’s a minimalist and highly recognizable logo.

9. **ESPN**: ESPN’s lettermark logo features the letters “ESPN” in a bold, sporty typeface with a red and black color scheme.

10. **NASA (Meatball Logo)**: NASA’s “meatball” logo is another famous lettermark that combines the initials “NASA” with a circular design containing stars and a red, swooping vector.

These examples showcase a range of styles and approaches to lettermark logo design. Each is unique and effectively represents its respective brand or organization.