Book looked good. Bought it. ... Haven't used it since.

[Ankh-Morpork Guard]

My Stargate SG-1 d20 book has just been sitting on the shelf...I'd love to get some use out of it, just not had the chance yet

 

[Halivar]

I purchased the XPH and have never used it. I really want to, though.

I also purchased the Planar Handbook; if I could do it all over again, I'd rather stab myself in the eye with a rusty screwdriver than buy that book. I couldn't really do that, of course; we all know time travel is impossible.

I do regret not being able to use psionics more, though. XPH is a really, really nice book.

 

[Psion]

I'd join the DDG chorus, but I sort of knew it wasn't going to be that useful.

Hmmm... Arcana Unearthed. Midnight (considering purging all my midnight stuff). Most big super-adventures (Necropolis, etc.) Eberron (but it was sort of my intention to check out the book and see if I wanted more. I don't.) Oathbound.

 

[the Jester]

Hmm, no real regrets, though some books are kinda overall stinkers (such as the Planar HB).

I've gotten at least a little use out of everything, even DDG (I used it extensively in designing my Ascendant epic prestige class).

 

[Old Fezziwig]

Creature Colection 1, SL: Ghelspad CS, and the two SL gazetteers -- not my bag. The 3.0 splats fall into this category as well (except for the pseudonatural template from Tome & Blood, which I used quite a bit).

Nick

 

[Sunderstone]

D20 Modern (lack of modules turned me off).
Dragonlance Campaign Setting (no use for this currently).
Mindscapes from Malhavoc (not a HC, too many Psionic rules revisions to date, If Thoughts Could Kill and Of Sound Mind are now useless to me).
Books Of Eldritch Might I and II (also not HC but remain unused all this time).

 

[Mercule]

DDG and ELH, but I expect to get some use from both, especially ELH when my PCs get to that level. Wheel of Time because no one in the group likes playing in "established" (aka, novel/movie) settings. Legends & Lairs: Wildscapes was the only 3rd party book that's captured my attension enough to buy, but it hasn't seen any use, yet, though it may.

If you open it up to non-d20 books, Amber Diceless tops the list. I've got a few WoD books that are in the list, too.

 

[Pseudonym]

Chalk up another one for the DDG and the ELH. In addition, in no particular order, are Relics and Rituals, FFG's Traps and Treachery I & II, Seafarer's Handbook and Spells & Spellcraft, OA and the entire Rokugan line and worst of all Enemies & Allies.

Related are d20 CoC and Decipher's Lord of the Rings. They sure do look purdy on the shelf and all, but I can count the number of times I've actually opened them on one hand.

 

[dren]

I buy maybe 3-4 hardcover a year and those I make sure by previewing them. There are a few things that I do not use during a game (MC's Arcana Unearthed) but they give me lots of ideas, so I don't regret buying them.

So, no, I don't think there's anything in 3.0 or 3.5 I regret buying. Everything I have I either extensively use or read through.

I find the best way to avoid buying something too hastily is never to buy anything in the first two months it's out. Read it over or preview it at your local game store/book store. Read online reviews (especially the ones here). Know what the books strengths and weaknesses are. Know your own game interests are...and think about if the book in question will this appeal to the style of game you like. I know it's hard to resist buying, but try.

There are lots of books, that if I was rich I would love to have (way too many to mention), but I can't justify spending the money with my limited resources.

 

[Bloodstone Press]

The Book of Vile Darkness. I baught it when ti came out. I read it. I liked it. I even had it used against me by another DM, but I haven't been able to use it myself yet in a game.