I know this may sound elementary, but after searching for over an hour for a good code for my budget rental I found this one on the specials tab of the budget website "$20-off deal" BCD Y620700
It was actually the best deal I could find and I tried all the BCD codes here. I got a 2 day rental for $39.99 compact (which was actually only $10 off not 20, but hey I'm happy!)