oboe
Orc, Olog-hai
ore ida
maybe okapi will fit.
A machine that starts with O is an oscillating fan.
Obsession
0bama
Ox.
Odey from Garfield
Olive Olwen
Oslo
oboe
Orchid
Orc, Olog-hai
outlaw
ore ida
It is an oblong which is another name for a rectangle.