Magnolias will probably always be one of my favorite trees to climb. It's also a very medicinal tree, nearly every part of it contains honokiol and other compounds are known to have a lot of medicinal value. Honokiol alone has been shown to have antidepressant, anxiolytic, antiemetic, analgesic, anti-inflamatory, antibacterial, anti-tumorigenic, antithrombotic, neuroprotective, neurotrophic, and serotonergic effects. Pretty awesome stuff in those trees.
http://en.wikipedia.org/wiki/HonokiolDon't see too many live oaks around here but I have climbed a couple, they are wonderful trees.