Hello ..
Can anyone tell me what this is ... I am hoping its the slave cylinder for the brake/Clutch...
but it does not look like the diagrams or pictures online
I tried bleeding it (brake pedal is going to the floor after taking out the ABS unit and putting it back)

 

I see from your profile you have a 2008 X-Type with the 2.2 Diesel engine.
Perhaps one of the Diesel X members can weigh in and help you on this question.

It does look somewhat like a one way valve "check valve" of some kind, and with the plastic spike on the end it must just connect into a rubber grommet or attach to a tube.
What does it connect to and from?

 

@Tomjones I'm pretty sure there is an abs control until under the battery box. Probably worth taking that out to get a better view of where the pipe runs.

 

Looks the same as a brake nipple. If it's connected to the brake system then it may be a way to bleed/drain the brake reservoir/pump..