1 of the things that bothered me,and I am sure it is pretty trivial compared to some of the other suggestions here,but my little boy and I just finished watching all 6 movies LOL and the thing that always got me from ESB is this(on top of some of the other examples already mentioned),when Luke just escapes from his Speeder and the Imperial Walker steps on it,it sure does NOT do much damage,in my opinion that Walker should just totally crush that Speeder,but it only crushes the canopy,not very realistic to me.
The Walker should out weigh that Speeder big time.
like I said pretty trivial,but it is always an attention getter for me.