I'll go ahead and mention the one that drives me crazy the most.
Why is it that C-3PO is made on Tatooine but doesn't know where he is in ANH? And how come Uncle Owen doesnt recognize C-3PO or R2-D2 when the Jawas sell them to him? Didn't he and his family take care of C-3PO for 10 years and meet R2-D2 in AOTC? Sure many droids look alike but surely they dont all have the same names, and surely they can recognize their former owners when they see them, just like C-3PO remembered the "Maker".
Oh yeah, and why doesnt Vader look for Obi-wan and his son on Tatooine or on the Lar's farm before/or during ANH?