ことがある/こともある => there are times when N5
ようと思う/ようと思っている => thinking of doing; planning to ~ N3
だろうと[思「おも」]う => I think probably A N4
Sentence Endings
ことだろう => Perhaps... N3
Speculation
たことがある => Have done A before N4
Situations and Experiences
と([思「おも」]う、[言「い」]う、[考「かんが」]える) => That A N4
Particles
と思う => I think N5
~であろうとなかろうと => whoever; whatever; however; even ~ N1
Innocent
ことだろう => how…!; what…! N2
Exclamatory
... だろうが、... だろうが => Whether it's ... or ... N3
Demonstrate by example
ところが => even so; however; even though ~ N3
たことがある => to have done something before; used to N5