via B-list:

iacobs@moria ~ $ history|awk '{a[$2]++} END{for(i in a){printf "%5d\t%s\n",a[i],i}}'|sort -rn|head
  238   bzr
   82   cd
   40   ls
   26   ./manage.py
   20   rm
   10   vim
   10   less
   10   firefox
    8   mv
    7   mkdir

just about right