My favorites are It`s fair and absolutely not. I use it every day. There are no new phrases for me. Here is a good list of expressions that you should not accept in English: in this section, you have a number of expressions that show you how you can agree in English in many different ways. My advice is that you read them, choose 5 or 6 that you particularly like and learn them from your heart. Also, I simply recommend not using “I agree with you” anymore, because it`s terribly easy and if you`re trying to pass a Speaking B2 or Speaking C1, it certainly won`t be enough….