Here is an updated list of the tools I use daily to try and make development both simple and enjoyable.
MacVim - I am back to using MacVim more than vim in iTerm2. I still copy and paste lazily and MacVim feeds that laziness.
MockSMTP - I know there are some free browser alternatives, but this thing is so damn simple to use, I love it.
CharlesProxy - If you really need to dig into a request, CharesProxy rocks (and no, the browser developer tools don’t count).
HomeBrew - install just about anything you need for development with ease.
OS X GCC installer - works perfectly with Homebrew and removes the need to install Xcode. My only recent issue with this was the rb-fsevent gem which appears to look for Xcode. You can fix that (temporarily) by using this branch: pre-compiled-gem-one-off
rbenv - I have only had a couple minor issues with RVM, so I decided to give rbenv a try. I have been using it for 3 to 4 weeks and so far it has been great (and solid).
pow - I don’t use Pow as much for active rails development (restarting rails too slow) but when you need to run multiple websites that interact locally it is amazing. In addition, it is a great way to host small local apps (like this blog).
zsh - sadly I am still noobish in the shell, but starting to get better.
Solarized - What I really love about solarized is having a consistent set of colors across multiple tools (iTerm2, vim, macvim, textmate, etc.).