As we all know Obsidian armor was 1 defence for a good week or so when Inferno was released, allowing pures to use it. It's since been fixed but this isn't the only items that need fixing.
Barrows Gloves (require 42 defence in quest exp to get in OSRS, from the current 40)
Rune Gloves (from 13 to 35 defence. I know you have to complete nature spirit + accept the Monkey Madness reward to get them)
Adamant gloves (1 to 13 defence)
Granite plate and legs, haven't checked helmet (1 to 50 defence)
Fremmenik helmet and shield, the ones dropped by DKs (1 to 30 defence)
Slayer Helmet and Slayer Helmet (i) (1 to 13 defence)
I'll add more if I come across them.