I rarelly use advanced functions of shells, things that are specific to them - so that my shell scripts should be shell independant as much as possible. But there is one thing that remains very shell dependant: the prompt. And having a beautiful prompt is an eye candy pleasure!
For that, Zsh shell seems to be the winner, although I did not looked too much in others. The fact is that, like many people, I choosed a shell years ago, and use it almost exclusively for interactive work.
So, about the prompt, I found some time ago the excellent Phil!'s ZSH Prompt. I modified it a little bit to be ACPI compliant and to not be aggressive for the filesystems (on AFS, for example, it can be important to cache the results of a find).
Here is my modified version, zsh_prompt, and two screenshots (click to enlarge them): one showing the prompt in action when you type in some commands, another one showing the difference between root and user prompts, and how it reacts when your current directory name is made of too much characters: