These are my top 10 in no particular order. They're basically what reside in my dock. I think you can really tell a lot about a person based on what apps they keep near.

1. Textmate 2. Transmit 3. Espresso 4. Adium 5. Tweetie 6. The Hit List 7. NewsFire 8. Safari/WebKit 9. Terminal + VIM 10. Pages