Does the @ prefix for delegates have any special meaning?

Some more details from MSDN:

The prefix "@" enables the use of keywords as identifiers, which is useful when interfacing with other programming languages. The character @ is not actually part of the identifier, so the identifier might be seen in other languages as a normal identifier, without the prefix. An identifier with an @ prefix is called a verbatim identifier. Use of the @ prefix for identifiers that are not keywords is permitted, but strongly discouraged as a matter of style.

from C# Language Specification: 2.4.2 Identifiers.

Prefixing with '@' therefore allows e.g. to derive from a class named "delegate" which might be defined in a library written in another language than C#.

In any other case I would not recommend to use this syntax and rather make up identifiers different from the C# keywords (e.g. valu instead of value) to increase code readability and avoid confusion whether there is any special meaning attached to it. If it is done, properly comment as to why it was done so that others are aware.

There is also another interesting fact about variable naming mentioned there:

Identifiers containing two consecutive underscore characters (U+005F) are reserved for use by the implementation. For example, an implementation might provide extended keywords that begin with two underscores.

The @delegate is to differentiate the variable name from the delegate keyword.