Oil
How Do You Get A Door Key Unstuck From A Lock?
This has happened to me twice during my life, and both times I was unable to remove the key from the lock without it snapping and being trapped inside! I then had to contact a locksmith as I was unable to enter the property.
I can't remember who I used the first time, but the last time I had this happen to me I used a company called Evander, who were quite reasonable price wise considering they arrived afterhours (www.evander.com/), but there are many other 24-hour locksmiths available should the same thing happen to you.
Thankfully a quick search on Google via your mobile phone will bring up local 24-hour locksmiths should the same thing happen to you :o)
When I saw the locksmith remove the key from the locked was he actually took the lock off the door so he can get to the cylinder. Once he got the cylinder we were able to see the other side of the lock and was about to pull it out.
Oiling or lubricating the lock with some oil based spray or grease or even rock oil should help. You can wait for some time till the oil is well absorbed and then try again. Care should be taken not to apply extra pressure or force to the key as the same may break and then it will be harder to work with the same. Special lubricating sprays such as WD40 are also widely available and are pretty good at this. If the key is moved to the position where it is entered and removed a pointed object can be inserted at the other end to push it out. This is only possible in a lock that is accessible from both ends. Locksmiths usually keep the necessary tools to remove the key and in locks built into doors they can even disassemble the lock itself.