I hate the key fob for my 2010 XJ. It works OK and I have two of them. But they're bulbous heavy old things, and they're all scratched. I didn't like the XF fob much either, but at least it wasn't heavy. Are there any alternatives?

 

No. The key is electronically mated (paired) to the car. Only a Jaguar XJ (X351) Smartkey will work.

You can replace the scratched case with a new one and simply swap the electronics from the old key into the new case. Or you can buy an inexpensive silicone cover, like I did, from Ebay.

 

A search of the x351 forum will give you additional information that the newer fob tyhat will work, but you will need a dealer or someone with a programmer to program any additional fob. Be aware that if you want to retain the old fobs functionality you will have to program all the fobs at the same time.