Ask HN: What's your favorite startup logo? Posted by tburger on Tuesday December 16, 2014 @10:11PM from the ask-hn dept. ( 3 comments | 10 points | on HN )
The Github Octocat is also awesome :)
https://octodex.github.com/
A couple of my favourites: Birchbox (birchbox.com), Treehouse(teamtreehouse.com), Intercom (intercom.io)