Sometimes ORA-600 can actually work for us ;-). Today, I powered on one of the PC’s that was offline for awhile and that it serves me as a test box. I didn’t spot anything weird until I tried to startup database to execute catcpu.sql from CPU Oct. 2010. I was greeted with the ORA-600 [2252] error:

ORA-600 lookup tool (MOS 153788.1) correctly reported (see MOS 138701.1) that I should check system time, since this error is raised when kernel detects system time that is very different from what kernel is aware of. I marked with the yellow the system time. Obviously CMOS battery run out of juice on this box and needs a replacement.
Doesn’t happen very often that ORA-600 works for me and not against me :).