One of the greatest strategy games of all time and also one of the most underrated culturally, XCOM puts you in control of an entire squad of customisable heroes, tasked with stopping an increasingly widespread invasion of Earth. However, that basic premise belies the brilliance within, as you're not moving your team around directly - instead as the omniscient 'Commander' you tell them where to go, what offensive/defensive positions to ready up, which items to equip and how best to press forward. The whole thing is done from an isometric viewpoint, and you'll uncover the map piece-by-piece, meaning the enemy could be anywhere inside. If any of your guys bite it (and they will) it's permanent death regardless of how many hours you've put in training them up, and that's not counting the brutal Iron Man mode; whereby the game auto-saves after every movement and instance, preventing those who were previously 'cheating' by reloading whenever something went sour. As any who've played will attest to, it's impossible to recommend this enough - just don't be surprised when the stray bullet that kills your lead Lieutenant affects your disposition way more than it should.
