Realized this hadn't been posted after seeing Daisy Disk on here. I have both on my machine, but don't touch Daisy Disk because Space Gremlin does such a better job showing me where everything is. Daisy Disk is certainly 'prettier,' but I get a ton more utility out of Space Gremlin.
I open it at least once / month to clean up my hard drive.
Space Gremlin
