i'd probably take one or two billion and buy myself a giant island to live on and forever take care of my personal needs. and fly into space a few times, too.

after that, i'd take the half of the remaining and invest it in technology and fields that i'd like to see improved (i.e. space travel, science, alternative energy, etc etc)

i'd take the other half and invest/give it to more charitable devices (poverty relief & research, disease research, land preservation funds, etc etc)

basically, try and make the world a better place.