Super angsty starters! I love this sort of thing, little prompts, it's fun! Anyway, here's the list- found it on Tumblr, credits to respective creator!
"You... did this?"
"I can't believe you."
"You can hate me, you can dislike me, but how can you cheat on me?"
"I'm dying..."
"She/he still loves you."
"I just want to go home..."
"You left me..."
"I can't forgive you for this anymore."
"I'm saying goodbye."
"I'm not good enough for you."
"This is goodbye."
"Was this just a game to you?"
"You merely played me like a fool."
"Goodbye."
"You're pathetic."
"Get out of my sight."
"You're nothing but a toy in a game of life."
"You used me?"
"You're so easy to manipulate."
"I never loved you."
"Don't give me that look."
"I can't stand you."
"I would have loved you."
"Everything fell apart and I can't pick up the pieces anymore."
"I think this is where I should say goodbye."
"We never had it all."
"Everything hurts."
"Go away!"
"I don't want to see you anymore!"
"Let me go."
"To think I almost loved you."
"You cheated?"
"You love someone else other than me anyway."
"Why do you even bother with me anymore?"
"I'm not worth your time."
"Get out of here."
"Get away from me!"
"Don't touch me ever again!"
"I hate you."
"Don't leave me."
"Please, I'll do anything!"
"Don't go..."
"We can talk about this!"
"I can't lose you again."
"Don't you have more important things to attend to?"
Pick one! :D