I found two pronunciations for the same ending (ugh), one sounds like F, and the other one sounds like omitting of the ending ugh.
That's what I found and you're happily invited to edit this post and to add more examples or change incorrect examples:
Sounds like f: though, tough, cough.
Sounds like omitting the ending: bough, dough, thorough, slough, through
Sounds like p: hiccough
Anyway, I couldn't find a rule which can explain when it should be pronounced as p, f, or be omitted. Is there such rule?