As per Dive Into Mark.

As zachhale

tarsi:~ zachhale$ uname -a
Darwin tarsi.lan 9.2.2 Darwin Kernel Version 9.2.2: Tue Mar  4 21:17:34 PST 2008; root:xnu-1228.4.31~1/RELEASE_I386 i386

tarsi:~ zachhale$ history | awk '{a[$2]++}END{for(i in a){print a[i] " " i}}' | sort -rn | head
81 git
65 cd
46 nano
44 cap
34 ssh
31 ss
23 ls
20 scp
15 sudo
11 mate

As root

sh-3.2# history | awk '{a[$2]++}END{for(i in a){print a[i] " " i}}' | sort -rn | head
77 svn
44 ls
30 cd
18 pwd
11 sudo
10 nano
10 mate
10 cp
10 apachectl
7 mysql

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