Flemke's F1 is #040, a good choice; It'd certainly be in my top 5, maybe even my top 3.
Different factors may decide people's favourite F1 - styling, history, personal experience, pedigree, vision / innovation etc.
If I had to stick my neck on the line to choose the best out of each of my categories above, they'd be -
Styling - XP4
History - XP5
Experience - #013
Pedigree - #01R
Vision / Innovation - #040
Favourite GTR (short tail) #13R
Favourite GTR (Long Tail) #22R
Favourite road car with HDF kit #018
Mind you, my favourites change fairly often, so [some] of these choices may be outdated soon