Two items to add to the list

(1) Add $(!!), recomputes last command

Comes in handy for things like these:

```
$ which python
/usr/bin/python
$ ls -l $(!!)
ls -l $(which python)
lrwxrwxrwx 1 root root 7 Apr 15  2020 /usr/bin/python -> python2
```


(2) Or find filename on whole file system, suppressing 'Permission denied' errors:

`find / -name filename 2>&1 | grep -v 'Permission denied'`
