No other four letters in English cause this much chaos.
throughTHROO
Sounds like "-oo".
thoughTHOH
Sounds like "-oh".
toughTUFF
Sounds like "-uff".
thoughtTHAWT
Sounds like "-awt".
boughBOW (rhymes with cow)
Sounds like "-ow".
coughKOFF
Sounds like "-off".
enoughih-NUFF
Sounds like "-uff", same as "tough".
hiccoughHIK-up
A variant spelling of "hiccup" — sounds like "-up".