Simply you've to add a new attribute called "font_face" in "Preferences" / "Settings - User" and give the value as per your font name you want to change.
Note: Removing this attribute will change the font to the default.
For more tricks, visit http://goo.gl/lDZ6Z3.
Screencast number #2 from http://SeeBeeTee.com
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Sublime text, Sublime text 2, Sublime text 3, Coding, Text Editor, Change the font in Sublime Text