Depends entirely on my character (and sometimes transmog). For my Mage (this character) I think I will always use “the Insane”.
For my Warrior I like using the Knight title with the BFA S1 Elite Glad set. Crusader for my Paladin. Deathlord for my DK.
For my Hunter I use “the Horde Slayer” when I am using my R14 armor set.