Pure Battlefield NES: something I've never done before because I ended up putting loads of crazy plot elements into NEB1. A hex-based, small map, futuristic battlefield with tanks, troops and VTOLs ('Battle Isle' style). Balanced start, two opposing forces with two overall commanders, but units split between an even number of players, very limited reinforcement, limited air/artillery strikes, no resources except 'supplies'. Its all about choosing where and how to attack, how much to risk, try to encircle and cut off their supplies etc.
Horror NES: crazy role-play in a near-future world where monsters, UFO sightings and time/space anomalies are much more common, plus there is an ongoing underground covert-ops war between rival factions of the New World Order. Players can search for 'locations' around the world and go these places to compete for 'investigation points' while trying to preserve their 'sanity'. Monsters and traps to be fought or avoided using items and special skills. Part Half-Life, part XCOM/UFO Defense, part X-Files.
Energy NES: Like NESLife, but with energy beings in another dimension, and so realism is not an issue. 'Species' can now have things like energy beams and teleportation, and can assemble together to form strange composite beings. Only NPC species can be evolved by other players, and species can be given specific orders to attack or ignore others etc. A map could have various energy sources and anomalies, and maybe 2D planet-like things that can be landed on and burrowed into.