Publishers, editors, magazines and competitions have all manner of topics for writers to submit against. Sometimes there are some strange or unusually specific ones:
“Powerful abusers in a self-correcting universe”
“Romantic gay fiction involving dragons”
“And You Think Razor Wire Will Keep Me Out?”
“What happened in the real or surreal lives of the old pulp heroes of the 1920s, 30s and 40s”
“Wage Slave Orgy”
“The Potty Mouth’d Rebellion”
These are just the ones currently active on Duotrope.