For the hitch receiver, I have tried a number of hitch pins, and the best I've found is a Bolt lock. It keys itself to the vehicle's key (means one less set of keys to keep track of), is extremely well made (automotive lock, same design as on doors), and is very easy to install and remove, almost easier than a hitch pin that uses a cotter pin.
The Bolt lock is one of the few things I really have found worth touting and worth the cash.
Downside is that it can't be rekeyed. It stays with the vehicle forever once the first key is inserted.
