There isn't any devices that come with ubuntu pre installed.
As of now, there two option to run ubuntu.
- Install desktop ubuntu and use with VNC
- Install ubuntu touch.
Install desktop ubuntu and use with VNC
This is quite steps need to be done to running this. At end it is not very usable.
Install ubuntu touch
Ubuntu touch is operating system developed for small touch devices. read more here http://www.ubuntu.com/phone/
Both method wants devices with open (unlocked) bootloader.
For this, I suggest google nexus devices. As those are open and ubuntu touch images are ready to flashed.
Here is more details : https://wiki.ubuntu.com/Touch/Devices