Scratch

No really, it's just that good. 

The puzzle piece idea is good, but Scratch lags if things get complex.
Everyone hates Lag, fix that please.
I also hate that the screen won't scroll up or down while I'm dragging a piece of code.
That could be fixed by adding a real cut and paste ability which would be nice to have in all aspects, meaning in the sprite editor as well.

Ok, on to the idea ... drum roll please .... tatatatatata tshhh!

The ability to Switch Modes at any place in the code and back again from several different options. Lets say you are working the puzzle piece style, you then switch modes to a FLOW-CHART style! and the 'then' code could surround the 'if' code on all sides, making things easier to understand. The lines going from the Circle or Square or whatever other Flow-Chart item should be adjustable to ANY length.

The reason for any length lines would be so once you start a flow-chart 'if', you can have that "if" point to several different (here's where the mode switch happens) puzzle piece codes surrounding it, so it spreads out then down, or have more flow-chart style code surrounding that and leading other multiple paths to code.

For each 'if' the 'then' code should all happen simultaneously like electric current following the lines, except that the length of the lines should have no bearing on the time 'then' events happen (although an ability to click near/on the line and set a delay for when the 'then' code that it leads to actually activates may be very useful.

Also in this mode selection idea, there should be a choice of a text style where the block code is just typed in. Another good choice could be C++ syntax style, HTML syntax style, Squeak SmallTalk, and a variety of other popular scripting and programming language syntaxes. This would mean that it would be a perfect tool to learn a little bit of those languages syntax'. This would not mean any extra compiling or anything as I'm only talking syntax here so everything would be limited to what the regular puzzle-piece Scratch block coding can do. Of course that also means you most likely can't learn everything about those programming languages just by using Scratch 2.0, but that's ok.