I’ve been known to say that a Glock, with its lack of extraneous controls, is the best gun for someone with ADD. There are 4 controls (outside of adjustable sights) on mine: the trigger, the magazine release, the slide release, and the slide itself. In keeping with Rule 1 (and subject to the same exclusions), I know that whenever I pull the trigger, it will go bang, and if it didn’t, there was a failure in the mechanism or ammunition. This facilitates the best remedy for dealing with ADD, setting routines. In this case, there is no routine to set, really. Insert magazine, rack slide, align sights, and pull trigger. I don’t have to check the position of any toggle or switch, unlock a frame-lock, etc. This is the minimal number of steps necessary to operate a semi-automatic firearm.
I could cut back the number of steps by using a double-action revolver or by keeping a magazine inserted and a round chambered. But at the range, I have to eventually reload, and the steps needed to reload a detachable-magazine weapon are notably simpler than those needed to reload a revolver, even assuming speedloaders for the revolver. Press the magazine release, insert new magazine, release slide; all of the fine manipulations can be done by my master hand, leaving my off hand to insert magazine and yank the slide off the hold-back lever (and if I was willing to accept the wear on the slide lock notch, I could do that with my master hand as well). With a revolver, I have to release the cylinder, eject the empty cases, grab the speedloader, insert speedloader, close the cylinder. All of that is done with my off hand; leaving my master hand to hold the gun. For me, who is intensely right-side dominant (seriously, I am much less dexterous with my left hand; and my left eye is notably weaker than my right eye to the point that I can shoot with both eyes open with little difficulty), the less I have to do with my left hand, the better.
I suppose much the same effective simplicity is to be found in the 1911, with the grip safety and the thumb safety both being placed where the gripping hand will naturally fall, but there is the manual safety as well; and as a single-action pistol, I have to also be aware of the position of the hammer. Technically on the Glock I have to know whether the striker is cocked or not, but the position of the trigger will tell me that; I don’t have to look (and in fact can’t “look” at the striker). If the position of the trigger on a 1911 tells you what state the hammer is in, I will retract this last; I’ve fired a 1911-pattern gun once and only put one magazine through it.
Obviously, Glock is not the only provider of firearms with the minimal necessary controls, but their products are the ones I am familiar with.