Mos Def 3 1st. This rationality has prevented me from buying many "similar to what I already own" frags. For example, I didn't by SMW because I have 3 8.4oz flacons of MI (and one 4oz gold sprayer). I also didn't dive into the recent furious buying of Tauer's Desert for I found Chergui/FT to fit the bill in a similar fashion.
I guess I'd be guilty of #4 next (i.e. bought Tauer's Orris blind, bought 2 C&S no.88 blind, bought a 8.4oz flacon Vintage Tab blind as well, and these are just the ones off the top of my head (oh, the 2 FT were also bb).
Not sure what you mean by #5 though - if you mean buying just based upon the bottle shape itself, then I'd have to say "never" (a previous thread discussed this concept, and I stated in it that "I wear the frag, not the bottle").