I don't know if "favorite" is the word but the three tunes I tend to use most often, in no particular order, are as follows: Westminster, St. Agnus and Kilmarnock.
Psalm & tune combination [most often]:
Psalm 23 to Crimond
Psalm143 (2nd Version) to Heber
Psalm 147 to Thanksgiving
Like David's number of top three mighty men, I could make quite a list.But to narrow it down. Bishopthorpe, Moravia, Saron, Godre coed, Riverdale,Glasgow.