Hi,
i do like the Ship Infestation (think its called so) and the politic puppets most

Getting ships AND planets from your enemy is really nice
I only played against AI yet, the first game i played i didnt made any inteligence-projects until i got several Messages each turn, telling me that my pop is going rampage, producing nothing and creating new empires...well from that on i really had some planets only building intelligence-centers...