I've really started buying limited editions of everything I possibly can nowadays, unless the extra content isn't worth the money (I'm looking at you, GSC, releasing one of the most badass collectors editions ever with Clear Sky, but only in ex-USSR countries, while the rest of us get a crappy steel case and a poor quality map for near twice the cost of the normal game).
This also applies to CDs and movies, I've even started buying special editions of things I already own if I can find them cheap (the LotR DVDs, the Matrix collection). I even spent £100 on a rare limited production piece of Rammstein memoribilia (sp?), and waited 3 months for them to print more of the Voelkerball Photobook edition. Kinda regret it seeing as I'm growing out of their new stuff, but I'll probably be able to sell them on eBay for a fair bit.