Windows 10
Seen nothing so far that changes my mind that Microsoft is the new IBM. Long past it's sellby date. Relying on revenue from old product lines, and all their new stuff sucking badly. You only have to look at their current lineup of disasters: Xbox One, Windows Phone, Surface, Surface Pro, Windows 8, Windows 8 RT, Office 365.
I guess there are loads that have failed so hard, I have even forgotten about them.
How long will the share price stay good, until the market sees that not only Windows 8 has failed, but Windows 10 too, and the world has moved onto tablet computers that Microsoft aren't even remotely relevant in.