create a Default Non-Value or Option for drop down lists

Hi,
everyone.
Is there any way to create a Default Non-Value or Option for drop down lists that acts as "Null"? 
The default is the first value of the list? Can't I live it blank?

Any suggestion?

Hello xue_ze_feng,

I can help you with creating default non-value item in drop down menu. Do you want to increase space in drop down list from top?

Thank you,

Best regards, nuknspax.