See this.

history | awk '{a[$2]++}END{for(i in a){print a[i] " " i}}' | sort -rn | head

4605 cd
3576 svn
2141 ls
1701 ruby
1308 cap2
1066 ss
978 rake
867 sshb
688 rm
635 mate

cap2 is just my alias for Capistrano 2 (I use both 1.x and 2.x, since I'm lazy to upgrade some old Rails applications, ss is my alias for script/server. sshb is a shortcut for ssh with a certain port number for SSH daemons (i.e. -p 22) that we use in Bezurk (you know, security through obscurity).