Savage Core is a new set of Pulp Skirmish rules from Lucid Eye Publications that just screams "Hollow Earth Expedition" to me.
It is described as:
"28mm pulp skirmish rules for battles beneath the surface of the Earth... Savage Core is a fast play, competitive set of skirmish rules set in a primal land of savage warfare where clans battle for survival. Mature readers only, mature themes of primitive warfare."The factions currently available include: Amazons, Atlanteans, Cro-Magnons, The Jaguar People, Simians etc
This is a game that not only ties in to many of my interests (yes, the Simian faction is very reminiscent of Planet Of The Apes, and I wouldn't be surprised to discover that The Jaguar People have shades of a certain Tarzan story to them), but also fits quite nicely with my eclectic miniatures collection.
And, of course, there is the heavy overlap with one of my all-time favourite RPGs, the aforementioned Hollow Earth Expedition.
The Savage Core rules are £11.99 and can be purchased from Lucid Eye here, while a selection of appropriate miniatures (which include a lost explorer and a Nazi officer) can be found here.
Massive hat tip to +Gordon Richards for bringing this to my attention.