What is the biggest animal you think you can defeat in hand-to-hand combat?

This stems from a discussion at work. I figured I could take out any animal under 120 lbs and most people thought I was nuts, arguing how tough a pitbull or wolf is. Most people were thinking they could defeat animals in the 50–80lb range, like badgers and bobcats, but “tougher” (dumber?) guys sided with me. I think if a warthog or pitbull were attacking, while I may suffer terrible injuries I believe I’d emerge victorious. I kind of picture getting a righteous kick in the things head before it got to me, then just beating the shit out of whatever it is as fast as possible. What do you think you could defeat?