Airline travel vouchers.
On the return from a recent pleasure trip inside the US I was scheduled for two short flights to return home on a Thursday. I work for myself so I am flexible.
Long story short: I repeatedly volunteered to give up my assigned seat. In compensation I received 4 free nights in a hotel near the airport and arrived home with $2800 in vouchers from a major US carrier and a check for $800. Original ticket cost me a little over $400.