oblige

obscene

observe

obstruct

obtain

obtuse

offend

omit

oppose

oppress

obscure

Olympic

opponent

violent

arson

beckon

cannon

carbon

carol

colon

common

crimson

demon

dragon

felon

flagon

frivol

gibbon

heron

jargon

lemon

lesson

lion

mason

matron

melon

Mongol

parson

patron

person

piston

petrol

plankton

poison

prison

python

reason

reckon

ribbon

sermon

squadron

summon

symbol

talon

tendon

treason

wagon

wanton

weapon