Sometimes while using a pickaxe (tested on diamond only, and tested in the nether) and right clicking, will cause the pickaxe to Regen 1 use, or 1 point/level.
Below, forced crash report, with before and after screenshots of a pickaxe showing the bug.
Environment
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.7.0_21, Oracle Corporation
OpenGL: AMD Radeon(TM) HD 6480G GL version 4.1.11156
Duplicate of MC-1040.