Common words:
* on
* upon
* upon
* agon
* bacon
* bron (archaic for "brown")
* con
* don
* eon
* iron
* leon (a male lion)
* loon
* neon
* non
* phon (archaic for "sound")
* salon
* scon (a type of bread)
* son
* won
Less common words:
* adon (a type of Ethiopian food)
* albon (a type of white clay)
* bion (a type of biomolecule)
* blon (a type of blonde hair)
* colon
* cron (an old friend)
* demon
* dion (a type of ancient Greek god)
* faron (a type of ancient Roman garment)
* gaon (a type of Jewish religious leader)
* geon (a type of geometric figure)
* haon (a type of ancient Irish warrior)
* leon (a type of ancient Greek city)
* liron (a type of Israeli city)
* lyon (a type of French city)
* monon (a type of ancient Greek musical instrument)
* pcon (a type of particle physics experiment)
* phonon (a type of quantum particle)
* pron (a type of pronoun)
* scon (a type of bread)
* scon (a type of cake)
* ston (a type of stone)
* thon (a type of ancient Egyptian god)
* tyon (a type of ancient Greek city)
This is not an exhaustive list, and there may be other words ending in "on" depending on the dictionary you are using.