If I run this on OS X: 

```
last -10 | awk '{print $1}'

```

I get:
chop  

chop  

chop  

chrihopk  

reboot  

shutdown  

chop  

chop  

chop  

chrihopk 

How do I use sed or awk to obtain the most frequent user 'chop'?

ADDITIONAL EDIT TO QUESTION:  

Our local admin account interferes with the results (username: support) and often we have a new starter on a client box.  

How could I modify 

```
last -1  

```

to omit the following and return the last valid username: 

support  

reboot  

shutdown 

Thanks