I've found a way to get ADB working on Windows 8.1. The trick is to use Intel's ADB drivers instead of Google's. We're going to need to manually extract the drivers from the installer because it doesn't recognize Windows 8.1 (ironic).
Bonus: This method of install ADB drivers doesn't require you to reboot without driver signature enforcement (because Intel signs their drivers like a good company should).
1) Download Intel's USB drivers from Intel's website (or my attachment). I don't have enough posts on XDA to be able to post the link but searching "intel usb driver for android devices" on Google has the correct webpage as the first result.
2) Download 7-zip to extract the drivers (if you don't already have it installed)
3) Right-click on the setup exe inside the zip file from Intel's webside and choose "Extract here" in the 7-zip menu. You'll probably get a warning about copying over files etc. just click yes to all.
4) Now open Device Manager and find the "USB Composite Device" that corresponds to the Android device. It may help to enter the "Devices by Connection" view (in the View menu). You'll want to keep expanding the device tree until you find the "USB Composite Device" that is the parent of your ADB device (and possibly the MTP device too). When you find that, right-click and "Update driver software". Click "Browse my computer for driver software" and click "Let me pick from a list of device drivers on my computer". Click the "Have Disk" button and browse to the directory that you extracted the drivers in step 3 then select "android_winusb.inf". You should see a single entry that says "Linux device with multiple configurations". Select that entry and click next.
5) After that installs, you should still see the exclamation mark by your ADB device (or you should see the ADB device with a non-working driver). Now you want to do the same steps as in step 4 except this time you should see 3 options when you select the inf. Click on the "Android ADB Interface" option and hit next.
6) You may need to reboot for ADB to pick up the device (or restart the ADB server)
Hopefully, this works for you guys. I did it successfully with my Ouya and Nexus 7.