Other than "stop", "walk", and "pedal", "get up and push" is the only other option on my singlespeed! Other than that, pretty much what Chipcom said, edited to remove mentions of "gearing":
Starting from a stop, accelerating out of a turn or from slowing down for traffic/obstacles, climbing a small hill, to break up a long climb, to get over a climb, probably a few other cases I don't even think about.
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--Ben
2006 Trek SU100, 2009 Motobecane Fantom CX, 2011 Motobecane Fantom Cross Uno, and a Bakfiets
Previously: 2000 Trek 4500 (2000-2003), 2003 Novara Randonee (2003-2006), 2003 Giant Rainier (2003-2008), 2005 Xootr Swift (2005-2007), 2007 Nashbar 1x9 (2007-2011), 2011 Windsor Shetland (2011-2014), 2008 Citizen Folder (2015)
Non-Bike hardware: MX Linux / BunsenLabs Linux / Raspbian / Mac OS 10.6 / Android 7