Spitfire was one of the cooler ones I thought, and the classic Ms. America. Namora I think has longevity like Namor and was around back then. Sun Girl was another one with fire based powers, Silver Scorpion sounded cool...

Here's a list I found of Marvel characters created back then as well as characters created later on that were retconned into existing during WWII.

https://en.wikipedia.org/wiki/List_of_Marvel_Comics_Golden_Age_characters

~KL~