SciFi ships are harder to decide on - they each have their own idiosyncratic attractions . . .
Tardis, Fireball XLS are the earliest I can remember loving.
My Cobra III will always have a place in my heart! It got me to Elite!
The Hammerhead (Edit
: from Space Above & Beyond) definitely is a major contender -
I'd fly one in EM but then again it's competing with the BSG Vipers especially with their ability
to turn on a sixpence (dime to you Yanks!
) The Saratoga which hosted the Wild Cards was a
realistic space 'carrier' - more so than BSG, I think.
The Borg Cube(s) and the Moon sized mothership in Independence Day are bad-assed but sublime.
Serenity just because the story and the characters were superb and Serenity felt like a lived-in ship.
Nostromo because it was the first 'industrial' spaceship I'd seen and set the scene for gritty, real ships
rather than the floating hotels in Star Trek - the list could go on and on . . .
[Edited on 28-4-2015 by DaveK]