I find that the low battery warnings turn on way too early on Macs and I'm left with months of staring at a blinking bluetooth indicator. I have yet to find a way to lower the threshold but I did discover how to remove the blinking indicator. I just copy over the low battery image in the system folder like so. The images are still being swapped out but since they're now the same it won't be noticeable. You'll still get the low battery alerts but at least the icon won't blink anymore.

cd /System/Library/CoreServices/Menu\ Extras/Bluetooth.menu/Contents/Resources/
sudo cp lowbatt.pdf lowbatt.backup.pdf
sudo cp Bluetooth_Low_Battery.pdf Bluetooth_Low_Battery.backup.pdf
sudo cp BlueTooth_Connected.pdf Bluetooth_Low_Battery.backup.pdf
sudo cp BlueTooth_Connected.pdf lowbatt.pdf

It doesn't happen a lot, but sometimes a CD or DVD gets stuck in my mac and it won't eject using the keyboard or dragging it into the trashcan.

When this happens I just open the terminal and type the following command, which usually overrides whatever is blocking the disc to eject:

drutil tray eject

Although I'm not sure when I'd ever use it there's also a close command.

drutil tray close

I'm not usually on a Mac, but several people I work with are and periodically they need to flush their local cache. I'm just throwing this here because I keep having to look this up. Just open the Terminal up and type the following:

dscacheutil -flushcache