Worth the effort:
All of the Helmut Lang fragrances are worth it, although they have been discontinued for a short enough time that they still aren't absurdly overpriced ($40-60 usually). These include Helmut Lang EDC, EDP, and Cuiron.
CSP Safranier (Sultan Safron) is another really good one. It, too, is fairly easily obtained with just a little extra searching, although it is discontinued. It's by far the best safron scent I've come across.
Not worth the effort:
Yohji Homme is one I go back and forth about. It's a neat fragrance, but I don't know if it would be worth paying much more than retail price. It's gourmandy, but not as light as Hanae Mori (which seems a VERY wearable gourmand) and not as dark and heavy as New Haarlem (which is almost delectable).
One I think is definitely NOT worth the effort is Jil Sander Feeling Man. People talk about how wonderful this one is all the time and, while I think it's a neat fragrance, if I spent $100+ for it, I'd be really disappointed. It smells like an 80's designer frag, definitely not a lost masterpiece.