I asked a similar question, but where possible I try to copy the names already in the .NET framework, and I look for ideas in the Java and Android frameworks.
Util are the unavoidable nouns you attach for coordinating classes that contain no state and are generally procedural and static. An alternative is
You could get particularly purple prosey with the names and go for things like
Master, but as I said I prefer keeping it like the framework names you're used to.
Some other common suffixes (if that is the correct term) you also find in the .NET framework are: