What to do if you lost your key for your bicycle lock?

Can you get a bike shop to cut the chain/wire if you can prove the bike belongs to you or do you need a locksmith?

You would be pretty surprised how easily you can cut them if you really want to cut them. Does anyone near you have any bolt cutters? Even if you cannot get them with a bolt cutter even the beefiest of chains will fall victim to a hacksaw....you may need to go through one or two blades but it will get the job done in less than 10 minutes and normally within 3 if it is a cheeper chain or cable.

So:
Try with the bolt cutters....
if that doesn't work try with the hacksaw.....
at this point you should have the lock off, but if you couldn't do it with one of those two items call the ol' locksmith up and take care of it that way.

Oh and DO NOT LISTEN TO KATIE SKATERBABE: I hope you have enough common sense to know that trying to "chainsaw" through a bike lock is about as smart as flicking a lion's teste.

You can use: bolt cutter, hand saw, of hammer/mallet if you don't want to pay for a locksmith and simply pay the cost for another lock. But if you have an affection for the lock, or don't have the aforementioned you might be able to get a locksmith to do it or get help from someone at a bike shop... that carries bike locks....

But if you don't have a mallet, handsaw, bolt cutter or are afraid to use one, ask a neighbor, chances are they may have one....

You could go to a locksmith...or you could try to break it yourself.
If it's a U lock, I would try to get a long lead pipe and put it through the U, then pull and push as hard as you can to try and pry it open.
There's also a...metal grinder thing lmao I forgot what it's called but it's like a miniature circular saw, you can try sawing through it.
Or Bolt cutters if it's a chain.

Locksmiths are kind of pricey...but definitely worth it if you can get your bike back.
I've never tried going through a bike shop.

Is it a kryptonite lock? Try a pen tube..
http://www.youtube.com/watch?v=aaWMRXjEt...

...or a combination lock?
http://www.youtube.com/watch?v=zvfj4D8yU...

You dont need to go to a bike shop you can most likely just use your own cutters to cut the chain

just buy a bolt cutter cut the chain or wire and then, because you probably will not need it anymore, return it... hehehe

just chainsaw it off

two words: Bolt Cutter!!!