I've realized that's it's rather difficult to classify things as "overlooked." It's a rather broad categorization, and it is different for everyone. Sure, the Angry Samoans would be considered overlooked by someone who is real heavily into the original Souther Californian punk scene, but I am trying to dig up "overlooked" bands that are not overlooked for the genre that they fit in to, but for the fact that they were ahead of their time or something made them unique in their own era. Klaus Nomi doesn't count ... novelty acts don't count. Bizarre doesn't get you points in my "overlooked" rubric.
That being said, I think that Wall of Voodoo classifies as an overlooked band because they played in a style that no one else played in during their time together, and no one since has really copied them. Unfortunately ...
The band, although it is often compared to DEVO, was actually quite a bit different. They drew influences from cinema and film scores. So their sound is stylized like DEVO's, but it has a narrative feel to it ... it changes according to some plot that only the band members saw.
They obviously dug the great soundtrack composers (Morricone etc.), but also seemed to really like the post-punk bands of the time as their musical structure was definitely pop-based. Their Western-style guitar and ornate arrangements combined with cold drum machine beats and bizarre vocals to make for a much more artistic interpretation of the new wave music of the day. I like Dark Continent most of all their albums, but many people say that their follow-up LP, Call of the West was the best for its "Mexican Radio" single. Regardless, both albums are great.
Listen to Back In Flesh to get a good idea of their sound.