Macbook pro with:
* TextMate for code editing (with the Ack in Project/AckMate bundles for searching through a large codebase, and updated bundles for Ruby on Rails, RSpec, Cucumber, Shoulda, etc)
* rvm for Ruby version and gem management
* Terminal (nothing special added here)
* Quicksilver for quick tasks and app launching
* Transmit for SFTP or simple Amazon S3 management
* Photoshop when graphics work is needed (or sometimes Acorn when it's a simple resizing)
* Skype for co-worker coordination and calls
* OmniGraffle for wireframing
* Chrome & Firefox with web dev related plugins (web dev toolbar, firebug, rulers, color pickers, etc)
* Mail.app for all email
* GitX for easier viewing of repo history/diffs (one of the alternate forks with added features) - still mainly use CLI for day-to-day operations
* SequelPro - a great, free MySQL app for mgmt, queries, etc
* pgAdmin - the same as above, but for Postgres
* and iTunes for the background music