If I could be half man half animal, I think I would choose to keep my head and replace my body with a creature torso.
however, walking around with a Tiger head could be pretty rad, tigers have that commanding attractive look. Sporting a tiger head would probably allow me to integrate into society fairly quickly, either as a personal trainer or a courtroom lawyer.
If I were to replace my body, for pure functional purposes, I'd choose the body of a squirrel. The years I've spent watching these critters climb trees, run from dogs & steal birdseed from Grandma's feeder has given me a true appreciation for their talents. My one worry is integrating into society, with a stature that is just a few inches off the ground, conversation w/ humans would be difficult. I'd either have to carry a megaphone or develop a wicked set of charade skills.
An Ostrich body could be pretty fancy, I'd be a hit on the charity & social gala circuit, as long as I kept my feathers nice and tidy...........but Ostrich's seem to have that turkey gobbler leg skin thing going on, I'd be self conscious of that. I would probably be the first Ostrich on this planet to insist on wearing leg warmers as cover ups, or have an insane addiction to body moisturizing cream.