Oooh so many. lol
Thinking about it generally I think I would take most of the chocolate available back about thirty five years, so that it tastes now the way it did when I was growing up.
Specifically, I think I would change the fudge in fudge bars to have different flavours inside the chocolate.
There are so many flavours of fudge available, and yet the only type of chocolate covered fudge bar is the plain variety.
Imagine how wonderful it would be to be able to buy a 'fudge' bar and have a choice of mint, or cherry, or strawberry, or orange, or whisky/rum/ champagne, or chocolate, or rum and raisin, or raspberry and vanilla, or any of the other varieties you can think of. I think that would be amazing.