The Secret Invasion (1964)
Roger Corman was given the largest budget he ever had to work with up until that time by United Artists (approximately $600,000) to make this one. A lot of the budget probably went to the paycheck of some of the actors though so what remained wasn't that much.
Interestingly Corman's "original Dirty Dozen" makes up for the lack of budget in other ways.
Corman was used to working on a small budget and pre-production was very important to him which together with post-production turns this into a tight and fast-paced film that generally succeeds in hiding it's low budget and offering plenty of thrills.
Btw don't watch the trailer before watching the film as I just noticed it contains major spoilers.
