Although Resi 4 can be looked at as the first step away from what Resident Evil 'should be', the core gameplay was great fun once you got stuck in, and nailing headshots in anything never felt the same way again.
It's a revolutionary genre-definer whose intense over-shoulder gunplay culminates in the battle with one Jack Krauser; an over-muscled knife-wielding commando that even when looking at his pre-release character art you knew you'd be fighting him before the game's end.
Fighting in a labyrinthine set of corridors and open areas, the two of you hunt each other down in a blur of bullets and occasional quick-time event-based beatdowns. It's a very fast and frenetic fight, and the tension soars throughout - but it's when Krauser takes on his morph-armed demon form after a long battle and the game challenges you to defeat him in a strict three minute time limit that things go to the next level.
Get on the business end of Jack's knife too much at any point in this fight and it was a quick trip back to the save point too - with the whole setup making for this showdown being thoroughly despised by pretty much everyone who survived it.