Triceratops!
Okay so it isn't a triceratops but it is a three-horned lizard and it lives in my yard.
He is a Jackson's Chameleon.
http://en.wikipedia.org/wiki/Chamaeleo_jacksonii http://www.hear.org/species/chamaeleo_jacksonii/
Although there are wild populations around Hawaii, there aren't any known populations around where I live so it is a bit of a mystery how this one came to be in my yard. Probably some neighbor kid dropped him off in our yard after his mom refused to allow him to keep it. Anyway, it appears he's alone so no need to worry about being overrun by chameleons any time soon. Hopefully he'll stay around and help control the pest bug population. That would be nice.