Make use of ExcludeFromCodeCoverage .net framework attribute
there is already this attribute in framework, most of code coverage tools make use of it, why not to use it.
NCrunch does already detect the presence of this attribute. On methods that declare it, NCrunch will not instrument them.
Note that there is a hole here - the attribute cannot be applied to inline/generated methods that are created from lambda expressions. There is no way to implement such support without a significant performance hit. Other tools also have this limitation.