1'; drop table user; --

Security. Student. 8CB2 3C56 1BD4 74E5 FB91 8EF8 8B6F 9890 10F7 0975

I sadly forgot where I found this snippet, but it lists your most used commands in the shell.

history | \
  awk 'BEGIN {FS="[ \t]+|\\|"} {print $3}' | \
  sort | \
  uniq -c | \
  sort -nr | \
  less

Wonder how accurately this could be used to identify users on a shared server…