It would be really useful to represent system values to be used in code as constants rather than having to hard code integer values.
This means that lookup tables can use nice tinyints as the surrogate PKs but when referenced in code the code can use the textual representation.
Essentially data driven enums.
I am happy for the restriction that this only applies to read only data.
an example where this wouldbe useful is the system message types/contracts in service broker. Currently you have to have strings like 'http://schemas.Microsoft.com/SQL/ServiceBroker/DialogTimer' in your code. which means you are comparing against 59 byte string rather than a 4 byte integer.