something tropical or maybe subtropical - nothing like a juniper or a maple or any of those - those wont be happy indoors for very long...
to start off some possibilities (which others I'm sure will add to):
1) several types of ficus
2) the hawaiian umbrella tree
I'm sure those are the 2 that most people will suggest first - they are pretty easy to care for, tolerant of indoor conditions and hard to kill (for most people
) they are also attractive looking trees if cared for correctly
anyone have any more options to add to the list?