I believe I mentioned this series in another thread a few years ago, but here goes again... Quark!
It didn't last long, but it was a childhood favorite and left quite an impact on me. Fun show. When we played Quark on recess (yes, we actually played Quark!) I was always Ficus.
I'd also love to see figures based on the old "Gargoyles" TV movie starring Cornel Wilde and Bernie Casey.
Gargoyles (TV 1972) - IMDb
Frankenstein Jr. would be another cool figure... maybe a 24" one with an 6" Buzz to ride on his back.
You can also add my name to the small but vocal list of "Monster Squad" fans!
And finally, I would kill baby seals to see a line of "Hawk the Slayer" action figures!
As for some properties that might be a bit more "mainstream" or recognizable to the general public, I'd love to see "Land of the Lost", "Night Stalker", "Lost in Space", and "Ultra Man".