Thank you @herrbischoff for creating this A curated list of shell commands and tools specific to OS X and functions.

Here area a couple of my favorite commands:

Safari

Enable Develop Menu and Web Inspector. This is great because it's always a pain to figure out where to turn things on and off within Safari preferences.

defaults write com.apple.Safari IncludeInternalDebugMenu -bool true && \
defaults write com.apple.Safari IncludeDevelopMenu -bool true && \
defaults write com.apple.Safari WebKitDeveloperExtrasEnabledPreferenceKey -bool true && \
defaults write com.apple.Safari com.apple.Safari.ContentPageGroupIdentifier.WebKit2DeveloperExtrasEnabled -bool true && \
defaults write -g WebKitDeveloperExtras -bool true

Spotlight

Erase Spotlight Index and Rebuild. I do like Spotlight and this makes it easier to index an external drive or maybe something on a network.

mdutil -E /path/to/volume

Search via Spotlight

mdfind -name 'searchterm'

Files

I can't stand .DS_Store but this little script makes my life super easy by recursively deleting .DS_Store files.

find . -type f -name '*.DS_Store' -ls -delete

DHCP

Renew DHCP Lease is helpful when you're doing full-stack web development.

sudo ipconfig set en0 DHCP

TCP/IP

This outputs all applications currently using port 80. Super helpful!

sudo lsof -i :80

Show External IP Address keeps me from having to open up a browser and visit http://www.whatsmyip.org/.

dig +short myip.opendns.com @resolver1.opendns.com

Show Local IP Address keeps me from having to open up System Preferences > Network.

ipconfig getifaddr en0

Wi-fi

Show Wi-Fi Connection History is really handy if you do lot of work at coffeeshops.

defaults read /Library/Preferences/SystemConfiguration/com.apple.airport.preferences | grep LastConnected -A 7

Audio

Convert audio file to iPhone ringtone is like the coolest thing ever!

afconvert input.mp3 ringtone.m4r -f m4af

Create Audiobook From Text is great for Podcast/Audible lovers like me.

say -v Alex -f file.txt -o "output.m4a"

Hardware

List all hardware ports is helpful if you're doing work with Raspberry Pi or Arduino.

networksetup -listallhardwareports