Turkeys and coyotes are smart and elusive. But for something big, fast, smart, hard to kill and bloody dangerous, how about feral hogs? Especially the ones that have cross-bred with European wild boars and combine the nasty features of both. I never had a chance to hunt them, and I'm too damn old and crippled-up now, but that looks like one hell of a challenge even with dogs.
"Don't let macho be your epitaph."