Using the right tools to get things done is the difference between daily frustration and seamless day to day work. As I develop Ruby applications and build products, I've found the following tools to be the most important in my day to day.
OS X — The Unix-like system is great for development, but the 3rd party software provides a real reason to stick with OS X.
Slack — The best way to chat with a team around. Tons of integrations and it really encourages you to organize conversations into the channels, making it easy for everyone to stay up to date at their pace.
iTerm 2 — It offers advanced configuration and workspace setup that becomes invaluable in your terminal replacement.
Alfred — I even swap OS X's spotlight with Alfred because it's faster, more flexible, and more powerful.
CodeRunner — This is my scratchpad for trying code in new languages and prototyping snippets in familiar languages.
Icon Slate — Favicons. Retina favicons. I'm sure you could use it for other icons, but that's all I use it for, and it's perfect.
Postgres.app — I use postgresql as my RDB of choice and love the simplicity of using Postgres.app to start and stop it during development.
Tweetbot — Mute, filters, countless integrations, multiple windows.
Sublime Text 3 w/ Vintageous — I've recently replaced MacVim with Sublime Text 3. The plugin ecosystem for Sublime is phenomenal, it allows me to easily pair with the less Vim inclined, and Vintageous lets me feel at home.
Hi-Tec-C Pen — The Pilot Hi-Tec-C pen writes smoothly with a super fine line that's perfect for both writing and sketches.
13" Retina MacBook Pro — After Apple upgraded the power and battery life of the 13" rMBP I made the jump, and it's been worth it. The slight sacrifice in portability from the 11" Air is more than made up by the sharp screen with ample space for development on the go. There's even enough room to use Xcode!
iPhone 6 — Thin, light, works seamlessly with my Mac.
AIAIAI TMA-1 Headphones — They block outside sound, and make electronica sound wonderful.
Audioengine 5+ — Sometimes headphones are too bothersome, and I have the opportunity to play music outloud. These speakers make my ears weep with joy.
Tonx — I'm pretty sure that no good developer tool list would be complete without something related to coffee. I've been consistently impressed with the consistency of bean quality, customer service, and coffee related attitude of this service and would highly, highly recommend it to anyone that wants to try a new coffee every week.
Dropbox — Everything is everywhere all the time.
Backblaze — And just in case it isn't quite everywhere enough.