I am not going to go into specific cards or strategies. What I want to communicate here is why you would want to play William Yorick, and what you can expect when you decide to send him against all the horrors of Arkham and beyond.
No investigator is perfect, and William Yorick is no exception. He's no great cluever, even though he has plenty of Survivor tricks to get by in a pinch. He doesn't have access to the big blue weapons either. Economy can be an issue, but that's par for the course for most investigators, especially fighters. He is not the fine-tuned precision instrument that Roland Banks can be, nor is he the awesome overpowering sledgehammer that Mark Harrigan is. But no investigator can give you the visceral (almost sadomasochistic) satisfaction of enduring what the game throws at you, spitting in its face, and shoving it right back down its throat like Billy can.
Control is the name of the game here. Read that little under his stat-line again, and maybe a few more times if you really need to. It is exactly as amazing as it reads. Once he has an asset, it's never really lost to him, in hand, play, or discard. A card in the discard might even be best place for him, providing for some of the best action compression this side of a federal agent. This control is what separates him from his color counterpart Tommy Muldoon, who is so much more at the mercy of his draw, and does not gain tempo putting them into play.
The Gravedigger seems at times less a man and more some stitched-together Leather and Cotton golem come to make war on the monsters of the Mythos. Where so many combat investigators are one bad treachery test or token draw away from the edge of insanity, this failed actor can grind through the worst the game has, dealing damage and protecting his teammates all the while. Yorick is the rare investigator who can simply outlast the game.
Assault the mythos with your preferred assortment of cops, cats, and curiously resilient old ladies. Have a whirlwind romance with a witch hunter if that's what the script calls for. Pick your weapon. Any weapon. You have the strength to use it well, and the durability to make sure you'll be around to as long as your team needs. Your weakness is just another chance to fire your ability. Your signature benefits the entire team during and after every scenario.
Whether you want to comically fling your kitties at ghastly ghouls or dramatically wade into battle with nought but a friendly teddy bear in hand and righteous fury in your heart, William Yorick can play the part. Against all monsters, terrors, and horrors, he'll fight, till from his bones his flesh be hacked.