I bought the Alex Anderson 4 in 1 tool, and put a bit of painters tape around the spindle that holds the end pieces on... haven't had any issue with them falling off when I go to use it now, and still easy to remove the ends when I need the tool on the inside. However, for the cost of the thing, I shouldn't have had to do that... but I would rather have to "fix" something and get it working properly than let it sit in a drawer not being used.
A couple of notions that I just recently got and am LOVING... the QTools Cutting Edge and Sewing Edge.
The Cutting Edge ones are vinyl strips that you put on the bottom of your ruler, along the line you want to cut. And it butts up against the fabric to keep it in place while you cut. I use that on my Creative Grids rulers. I do take my time to get it on as perfectly as I can, so it is straight and even... if you don't then it is useless... but when done properly it works great.
The Sewing Edge is also vinyl but with a sticky back, that you put on the bed of your machine, at your seam allowance, and it sticks. I have mine at the 1/4" and it lines up perfectly with the edge of my 1/4" foot, and much easier to keep the fabric straight going into the foot. Again, you need to take your time and get it lined up precisely, not just slap it on the bed and hope for the best, but when it is on there, it doesn't move. You may need to clean the machine bed with a bit of alcohol to make sure there isn't any dirt or oil so that it sticks well. I can't compare it to any of the other seam allowance type gadgets since I never tried any of them. But compared to just using the 1/4" foot, with or without a guide on the foot, I love the QTools Sewing Edge.
The prices for either of these is under $10, but seems "expensive" for a few pieces of vinyl, but since I got them and started using them, I absolutely love them.