The saving system and the tank controls. I have no interest in playing it (AND I own it).
Will wait to buy RE4 until the price drops, because I still haven't started 3 and have barely played 2 (again own both).
The Yakuza games was smart to go in proper order and so I'll probably get to these quicker. At some point I'll break down and play 2, but it would have been nice to play it sequentially.