I've been using Ack for a while, and really like it. It saves a few keystrokes, and gives you a nice (colored) output of the results with line numbers as well:

> grep -r unicorn .

./config/unicorn/unicorn_build.rb: logger unicorn_logger

./config/unicorn/unicorn_build.rb: old_pid = '/home/rails/xxxxx/current/tmp/pids/unicorn.pid.oldbin

./config/unicorn/unicorn_production.rb: '/home/rails/xxxxx/current/tmp/pids/unicorn.pid.oldbin'

> ack unicorn

config/unicorn/unicorn_build.rb

10:# logger unicorn_logger

14:# old_pid = '/home/rails/xxxxx/current/tmp/pids/unicorn.pid.oldbin'

config/unicorn/unicorn_production.rb

15:# '/home/rails/xxxxx/current/tmp/pids/unicorn.pid.oldbin'