Halo, like Smash Bros., is stupidly popular. Millions sold around the globe to eager Master Chiefs-in-training. And of those millions, a damn large chunk is obsessed with finding each and every game-altering skull, no matter how well Bungie tucked them away. Within minutes of Halo 3's worldwide marketing blitz, gamers scrambled to find 'em all and reap their benefits - if you consider making enemies tough as hell, grenade happy and invisible a benefit, that is. They're such an in-demand object that our Skulls Guide remains one of GR's most popular articles, seven months after the game was released. Pretty good for a severed, nameless head that just sits there collecting dust.
Collectibility aside, the skulls are also quite useful in multiplayer. They don't add new dialogue or make confetti pop out of grunts' heads as in single player, but they do deliver a one hit kill to anyone greedy enough to approach their owner. Just look at all those fools flying through the air, desperately trying to collect a measly skull. Any price is worth the effort - even a hilariously embarrassing death.
Obsessive: If you succumbed to Skull-o-mania, odds are you also spent hours perusing Liberty City in search of all 100 Hidden Packages. Amazing how such simple designs can instill an irrepressible urge to locate 'em all.