Sir Laurence Olivier famously left Rosencrantz and Guildenstern out of his Hamlet. So, play director for a minute. Who else appears to be a major character that you think you could get away with cutting? You are allowed to give that character’s lines to other characters, as necessary, but you can’t invent new characters to compensate. No merging to create a new and unique character (so no blending of Tybalt/Paris/Prince into a single entity ala Sealed With A Kiss).
My first time directing, I actually cut Lady Capulet. It definitely changed the interpretations of Lord Capulet and the Nurse though.
Hecate.
Her two small scenes in Macbeth aren't even written by Shakespeare (Middleton added them when he revived the play in rep with his own "The Witch") so I felt no remorse in brutally excising her and her jangling verse from my production.
Lady Montague goes sometimes altogether. I read once that the reason she dies at the end is that Friar L was playing both parts and they all realized that she couldn't show up at the tomb with the Friar.
Fabian has been cut/combined with Feste.
You can combine Ursula with Margaret in Much Ado.
Paris sometimes disappears except as a concept in R and J. (See Zefferelli, who cuts his part quite a bit)