I am guessing you are referring to "Reserved Words" and special characters. Take a look at the following links, but ultimately reserved words and reserved characters are going to be more DATABASE (shapefile, MS Access, Oracle, SQL Server, etc) dependent vs ARCGIS dependent.
I don't know about a definitive, complete list, because it depends on the DBMS, but ArcObjects and arcpy/arcgisscripting have functions for helping you write valid SQL queries and validate table/field names. ArcObjects also has DBMS-specific invalid character lists.
Remember, too, that ESRI appends to names you give columns etc, and if you don't pay attention, you could go over the permitted width for columns, table names etc. I think 22 is the magic number on that. also, this will depend on the RDBMS you se, and each one will be different.
I've already find this explanation of Microsoft about reserved words for Microsoft Access. and....oh surprise!!! "LONG" appears!!!
List of reserved words in Access 2002 and in later versions of Access
This article lists words and symbols that you should not use in field, object, and variable names in Microsoft Access 2002 and later versions of Access because they are "reserved words." Reserved words have a specific meaning to Access or to the Microsoft Jet database engine. If you use a reserved word or symbol, you may receive an error such as the following:
The wizard was unable to preview your report, possibly because a table needed by your report is exclusively locked.
If you use a reserved word, such as date, value, name, text, and year, in Access 2007, you may receive the following message:
The Name you supplied is a reserved word. Reserved words have a specific meaning to Microsoft Office Access or to the Microsoft Office Access database engine
For existing objects with names that contain reserved words, you can avoid errors by surrounding the object name with brackets ([ ]).