cat ~/.bash_history | tr “\|\;\&” “\n” | sed -e “s/^ //g” | cut -d ” ” -f 1 | sort | uniq -c | sort -n | tail -n 20

It’s not perfect but will give you a rough idea.

On my own computer I get:
timp@shammah:~$ cat ~/.bash_history | tr “\|\;\&” “\n” | sed -e “s/^ //g” | cut -d ” ” -f 1 | sort | uniq -c | sort -n | tail -n 20
8 dig
8 fbsetbg
8 make
9 cvs
10 do
10 done
10 for
11 pwsafe
11 wget
12 rm
13 ./test.sh
13 vim
15 cat
15 svnadmin
16 grep
19 su
25 ssh
55 svn
83 ls
96 cd

A couple of things of note:

dig is similar to nslookup
You can also see that I often work with version control: svn, svnadmin, and cvs; I like VIm over vi; I use ssh a lot; and that it’s not unusual for me to use Bash’s builtin “for” loops (do, done, and for)