This is funny story, I tend to lock myself many times on the DEV system because of the wrong typing of the password. Mainly it happened when I switch the layout of the keyboard in Windows from Polish to German.
Normally it would not be a problem to ask your colleagues which is sitting next to you, to unlock your user, but because of the company policy, we cannot manage other IT colleagues accounts in SAP. So I was asking always Basis team to unlock me, but as I do it often, then I said to myself, that there need to be an option to unlock myself without bothering my Basis colleagues.
And there is one.
But there are two prerequisites - you need to have access to other system that has trusted RFC connection to the DEV system and you have to have debugging rights with possibility to make changes during debugging. In most cases I think this is standard for developer :)
OK, so here are the steps:
1. On system to which you have access go to SE37/SE80 and run ABAP4_CALL_TRANSACTION FM with proper RFC target of your DEV system and transaction SU01.
2. Put your user name into proper field, switch on debugging using /h command and click on unlock button. 
3. When the debugger window will appear, add new break-point for class CL_IDENTITY and method NODE_AUTHORITY_CHECK and press F8 
4. Once the debugger stops, press F7 to go out from the method and then change the value of the variable LS_MSG-MSGTY or LV_MSG_DATA-MSGTY from 'E' to empty. Presss F8. 
5. Repeat the step 4 after pressing the unlock button. You should be now unlocked :)
