For me, Creaure Collection. The horrible art and the poor D20 rules compliance really turned me off, and it sat on my shelf untouched for nearly a year and a half. Now that I'm reading through the SLCS, I've been looking through it a lot lately, and there are some really intriguing monsters in there.
Also, Rappan Athuk. I bought it back in the early days of D20 because I wanted a dungeon, and it seemd too old school and arbitrary to me. As I've gotten more DM experience, I now can't wait to get a chance to run some PC's through RA.
Also, Rappan Athuk. I bought it back in the early days of D20 because I wanted a dungeon, and it seemd too old school and arbitrary to me. As I've gotten more DM experience, I now can't wait to get a chance to run some PC's through RA.