Sometimes these things are so obvious that it's almost embarrassing to even mention them. But one thing I've learned since the beginning of the .NET era is that there is just so much to take in that even the really obvious things sometimes just aren't, well, obvious (at least not to me, anyway).
Here's one that you probably sussed out ages ago but I only found by chance while doing something else.
You are in Design view and have a Windows Form on display. You select a control or a component from the Toolbox, but then you realise you don't want it - you picked the wrong one, you changed your mind about using it, whatever.
But, like a clinging ex-girlfriend, that darned icon is just stuck like glue to the point where your mouse cursor is pointing. You can't shake it off by clicking outside the form, selecting something in the Solution Explorer, clicking in the Error List box, passing it on to a mate .... (Oops, wrong scenario; must have been thinking about the old girlfriends again!).
You can't even fool it by clicking another window tab and looking at another form. Well, you can, but when you eventually sneak back to the form you started with, guess what's still clung to the cursor?
Yep, that darn icon.
So then I got to wondering why every Toolbox Tab has a "pointer" icon in it..... and there you go - you click on the Pointer and - oh, duh, you get a pointer. Your unwanted, redundant, ready-to-drop-just-where-you-don't-want-it, icon is replaced by a nice undemanding default pointer icon. Job done.
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Afternote: While fooling around with this, I also discovered that you can shake off the pesky icon by clicking on the Tab Name bar of any of the tabs in the Toolbox. But I kinda like the Pointer icon now that I've discovered it.