It seems to me, when I think back to the games we played as kids, that most of them were sort of sanitized imitations of war.  In fact, I guess that's what most sports are.

 Starting in about the fourth grade, we played mumbletypeg.  (We didn't spell it that way, but the dictionary does.  We spelled it mumble-de-peg when we spelled it at all.  Maybe I ought to look it up in a fatter dictionary.)  Anyhow, that was one of the kids' games that built on the essence of war — taking and holding territory.  It depended on two properties of the pocket knife that we didn't even think about in those days: the fact knife blades are flat, and the fact they'll stick in the ground if you throw them down right.

 Maybe kids still play mumbletypeg.  If they do, I've never seen them.  And I know I never saw my younger son and his friends play it.

 We'd start by drawing an outline in the dirt — maybe a big, wobbly circle (although some kids could draw circles that looked just about perfect) — or maybe some kind of polygon.  All that really mattered was that it was a closed figure.  And then we'd scratch a line across the playing area, dividing it approximately in half (assuming two kids were competing).

 If two kids were playing, one of them (it didn't matter which one) would draw the dividing line, and the other would choose his territory — one or the other of the two areas.

 Then it was time for the first throw.  The kid who'd won the toss threw his knife so it stuck upright (roughly) in his opponent's territory and so that a line extending the gash the blade had made would cut the initial dividing line — the "internal" boundary.  He'd draw that line, dividing his adversary's territory into two pieces, and cutting the original dividing line into two segments.  He would then erase one of those two segments, adding part of his adversary's territory to his own.

 Now it was the adversary's turn.  He'd throw his knife, draw the line that extended the gash made by his blade, and reclaim a piece of the other guy's territory.

 At any one point in the game, there'd be two territories inside the outer boundary.  The line that separated them could get pretty jagged, and sooner or later, one of the players would "own" most of the land.

 The key to the game was the rule about the line that you drew after you stuck your knife into the ground.  It had to be an extension of the gash the knife blade made when it stuck — an extension of the plane of the blade.  And it had to reach the boundary between the two territories.  If it didn't, no territory changed hands.  It amounted to losing a turn, because the other guy then got to throw again.

 As one player's territory shrank more and more, it got harder and harder for that player to throw the knife so the resulting line would reach his territory.  With really skillful players, though (or where the losing player happened to make a real lucky throw), a game could last a long time.  With just a smidgen of territory left, you might get just the right angle on your knife, so one end of the extended line did touch your land and essentially split your opponent's holding in half.

 If I remember right, a lot of those games were called on account of darkness .after the guys in my age group got good with their knives.

 There was one variation of the game I stayed away from.  As we got older, we tended to replace those first pocket knives with bigger ones (to fit our growing hands), and they had a lot more heft.  So one real "blood thirsty" variation was for one player to throw his knife into the ground, then for the next player to attempt to spear it with his.  If the second player made a good throw, he either knocked the first player's knife over or, with a very accurate, very hard throw, he broke the other knife.   As I say, I didn't take part in that variation.  I figured I was good enough to win most of the time, but I knew I wasn't going to get a replacement if my knife got destroyed.  I'm not sure if I was sensitive enough to extend that concern to the plight other players would be in.  In any event, I never did lose a knife that way.