Which tft works on both Arduino Uno and Raspberry pi Ideally I'd like a 2.8 inch and it to be touch screen. 
But most of all I'd rather it work on both boards without much hassle.
Well any display can work on both of the boards if you can adjust the voltage levels right there is a display which was made for old Nokia phones and it is called nokia-5110-3310 and  is dirt cheap display and it can be used with both Arduino or raspberry pi or any other board which support the protocol here is a link for quick reference. 

Adafruit link to the library