Things that get inside your bat and pad.
I'll start.
Bought a set of Srixon ZX7 irons 4-p off nudgee and used them for a month. Liked them but couldn't figure out why Srixon had decided to make the 4 & 5 irons so chunky for their 7 series. Went to sell them and the potential buyer pointed out that the 4 & 5 were ZX5 and it was a blended set.