Restrict Access to a Specific Item

I want to create an item that only certain users can select. Is this possible? And how?

Well almost, this is a bit tricky but depending on your set up it may or may not work. This can be achieved by using Contracts where under their Custom Settings tab you configure the system not to allow users to use this Item under this Contract. Then, when adding Charges under such Contracts "standard" users won't be able to select them while Administrator users will - they'll get a warning but will be able to continue saving the Charges.

Hope this helps.