BibDesk
Used by 4 peoplebibdesk.sourceforge.net ↗

“I use BibDesk to organize my library of papers.”
Victor Hanson-Smith Interview, Computational biologist · via Uses This 
“I tried using BibDesk to manage that stuff in the GUI (and store PDFs alongside the references) but it didn't take.”
Kieran Healy Interview, Sociologist · via Uses This