1. Han shoots first (and only).
2. Jabba scene removed from ANH.
3. Sebastian Shaw is Anakin at the end of ROTJ once again.
This is tough. I also wanted to remove all extra celebrations from end of ROTJ leaving just Endor, restore Luke's line about R2 not tasting so good in ESB, and also restore the dialogue between Vader and Palpatine in ESB. But the three above are much more important to me.