Non Obvious commands or missuses of common commands

Are there any commands like that? That is, are there any exceedingly mundane commands on some systems that have exceedingly jeopardous results on other systems? I used to define a lot of commands in DCL in my startup file that I commonly used and named them with weird names. I have accidentally typed the same command on a PC and ended up with unexpected results. After 5-10 years of using the command on the VAX I could barely remember the actual DCL. I also used nested command procedures. $GETMRI $DMPMRI $COMPRESSMRI $DECOMPRESSMRI $CLEAN My clean command deleted all files in the directory and removed any subdirectories. I once typed clean when I was in one of my source code directories. Lots of fast CTRL-C and slamming of keys trying to abort it. We were all logged in with lots of privileges which can be a problem. Mike mmcfadden(a)cmh.edu