I have a few swords (due to some silly SCA activities) but really my "favorite" sword depends on where I'm going to be swinging it (I used to do live steel choreography). Close quarters? Corridors? Some type of shortsword (the kelt leafsword for example) or "notquitelong" sword like a Viking sword (an evolved form of 8th C. spatha).
For outside work, a bastard sword ('hand and a half') because of its flexible use for one or two-handed work.
Katana are interesting to use because of the requirement for extra precision due to their one-edged construction but I'm a bit tall and long-limbed to use one as quickly as the people who invented them
I've never really been fond of piercing swords (rapier, etc) but that's as much a time period interest as anything else.