As the early 60s were morphing into the mid 60s, sci-fi offerings were no more numerous. '63 was a mix of low-budget quirkiness and better fare. Some of the old tropes get a retread and the Nazis make a surprising come-back.
Reptilicus -- Another Danish-American production, essentially Danish Tourism Board's version of Godzilla.
Day of the Triffids -- A British version of the classic apocalyptic invasion story, but with iconic walking man-eating plants.
Mantango: Attack of the Mushroom People -- Ishiro Honda's thoughtful tale of seven castaways who one-by-one start turning into giant mushrooms. Only one of them escapes.
The Slime People -- Low-budget invasion tale in which creatures from within the earth take over Los Angeles. Trapped within the invisible dome is a plucky band of survivors.
The Day Mars Invaded Earth -- Low-budget mix of Angry Red Planet and Invasion of the Body Snatchers. Energy beings from Mars replace a scientist and his family.
X: The Man With The X-Ray Eyes -- One of Roger Corman's best films. A doctor invents a drug that lets him see through objects. He goes too far and sees and is terrified at what he sees.
Madmen of Mandoras -- Quirky low-budget story of nazis hiding in a tiny South American country who have kept Hitler's head alive since 1945, and plan to take over the world.
The Yesterday Machine -- Another low-low-budgtet story about nazis. This time, a nazi scientist has invented a time machine so the Nazis can win WWII.