I agree with dougczar - this is a cracking question.
I think I'd have trouble with my attars, but the full bottles (around 120) I reckon I should be ok.
I think the two fragrances I have that smell most similar - at least according to discussions here - Sycomore and Encre Noire, smell most different at their opening, and I'm very confident I could identify them.
The only ones that would provide me any challenge would be the real cheapies - Antonio Banderas, Pal Zileri Lab, Corduroy (I don't smell much out of this, I find it really weak) and That's Amore. I just don't wear them very often and they DO smell unremarkable.