Minecraft 1.5.2, Minecraft 1.6.2, Minecraft 1.7.4
Stair break texture doesn't mesh up right.
Try placing a stair on any direction except f=0 (south), and breaking it (you cant be in creative for logical reasons).
The break texture should mess up.
(If it doesn't happen, try other directions, the f-system doesn't make 100% sense to me)