Turning Circle Templates — approx 35KB PDF. These are for use in aerial dogfight games, but I guess they could also be used in naval games, or sci-fi Road Warrior scenarios as well. I was originally going to get them laser-cut, but that proved to be too expensive, so I just glued the print-out to cardboard and cut them out myself.
I've been interested in wargaming since about the last Ice Age, when mighty mammoth roamed the plains and primitive geeks and nerds played games of skill, tactics, and interminable rules-lawyering about the campfire. I began when I was about 7 or 8, playing games without any rules with soft plastic 1/32nd scale Airfix figures and a spring-loaded Britains cannon which shot little plastic shells with potentially lawsuit-invoking force. Later I played games with a friend in his father's garage, in which the table was often so crowded with 1/72nd scale plastic kitset tanks that it was difficult to move them. Not long after, I discovered Heroics & Ros 1/300th scale microarmour, and we played equally unrealistic games with hundreds of them at a time, with mixed forces comprised of vehicles from every conceivable nation — no infantry though; they weren't glamorous enough, besides being too fiddly for our tastes.
I lost interest in wargaming for quite a while, being more interested in tabletop roleplaying games. Then, when we moved down to Christchurch I became re-enthused, this time in Medieval 25mm gaming — an offshoot of my penchant for fantasy rolelaying. I painted a lot of figures, but didn't actually do much wargaming; I suppose I've always been more interested in the modeling side of the hobby than the gaming. I ran a reasonably successful multiplayer campaign for a year or so, but in the end I became disillusioned with the constant bickering over minute points of the rules, and gave up wargaming altogether.
I've regained some interest in wargaming, mainly by staying away from rules lawyers and those for whom the joy of the game is in gamesmanship. I don't mind playing with people who play to win, but if winning is the only joy they get out of the game, I find they're generally not much fun to play with.
My main interest, as far as rules go, are in the various sets produced by Warlord Games: Bolt Action for WWII, Black Powder for the musket era and early rifles up about 1900, Pike & Shotte for the late Renaissance and English Civil War period, and Hail Cæsar for ancient to medieval gaming. The reason they appeal to me so much is because they're designed primarily with having fun in mind. They're fairly simple, but not overly abstract, and they're easily modified if you want to add detail or expand genres — Hail Cæsar, for example, is easy to adapt to fantasy wargaming with a few simple additions and by adapting the base rules.
I do a lot more board gaming than miniature wargaming these days.