I recently came across Brink of Battle: Skirmish Gaming through the Ages, a set of wargame rules that has been around since early 2012. It is intended to be a game for small skirmishes -- at most 20 figures per side, individually based -- set at any time from 3000 B. C. to the present day. It certainly is a tall order, something the author Robert A. Faust admits right at the beginning of the book. Mr. Faust also emphasizes that this is meant to be used to play historically-based conflicts, including "what-if" scenarios but no sci-fi or fantasy (a fantasy supplement has been announced.)
In order to accomplish its goals, the game splits history into three periods. The first goes from antiquity to around 1450. The second one goes from that moment (with the rise of gunpowder) up to 1880. And the third takes up from that point in time to the present. The periods determine available equipment and special abilities that the units may possess.
There is a very detailed review of the game at the blog Anatoli's Game Room and I would advise anyone interested to read that post. Rather than repeat those words (with which I mostly agree) I will only comment on a couple of features that got me very interested. First is the fact that the rules were written with tournaments in mind. If, on one hand, this makes them a bit dry to read, on the other hand it is possible to find carefully defined procedures that were intended to avoid conflicts between players. One example are the targeting rules. As a result, the player is given a good framework to get started with setting up solo play house rules. The other feature is the uniform and clever use of a single die roll mechanic and penalty system, complemented by a simple damage system. These make the rules easy to grasp and to remember, with very little need for paperwork and rules lookup.
I still have to play actual battles with this system (so far I have only run very quick tests to learn the rules) but given its features and flexibility, I believe that it will join the set of my frequently-used rules.