I've never actually observed any celestial objects through a telescope!
I did however vote on Saturn, from all those days in primary school 'reading' those solar system books in the library and just being impressed. Venus was also pretty cool - except I always found it a little exasperating having none of my classmates believe that it was hotter than Mercury!
On Mercury - I also like the messenger! I didn't realise how visible it could actually be until I bothered to look at the right time of the year.
Greenish Uranus is awesome for being on its side and all... But again, the aspect of primary school's peer-reviewed-opinions doesn't really lend too much respect there.
I guess it's Saturn for now until I get to actually watch Jupiter's spot and satellites for a while.
io.