If you were asking your clients to rate your service (and you are doing that, right?), you could ask them to use the traditional ABCDF scale, or, you could use the Zinn-Segaran Experiential Grateness Scale:

0. Forgettable.  Events that could be forgotten and have no impact on your life. A typical example is a regular morning commute, which people often cannot recall at all due to having spent the time daydreaming about other things.

1. Inconsequential.  Many day-to-day events occur at this level. Running into and greeting a neighbor on the street, an uninteresting work project or a mediocre meal at a diner are all inconsequential. These events are distinguished from "forgettable" by the fact that they are usually remembered briefly, but usually not considered.

2. Eventful.  Experiences at this level are moderately memorable, and will possibly be discussed by those present for no more than a day or two after they occur. They are unlikely to come up in conversation with others except in responses to specific questions like "what did you do last night?". Usually active concentration will be required to remember much of the event a week later.

3. Noteworthy.  Noteworthy experiences tend to elicit a fairly strong emotional response at the time whether confusion, amusement or anger. Usually the subject is eager to share them with others in the following few days, even without being prompted.

4. Significant.  When reminiscing about important things that happened in the past year, most events that are recalled will be significant. Typical examples include winning a minor award or totaling one's car without serious injury.

5. Remarkable.  Remarkable experiences are those that have a strong impact on behavior or change strongly held views. They may not always be remembered, but they stick with a person in a meaningful way through their outlook and opinion.

6. Exceptional.  This is the lowest rating at which things will likely be somewhat memorable for one's entire life, and recalled on occasion with a moderate emotional response.

7. Monumental.  These experiences are always remembered and likely to be discussed with those present for life. Oblique references to stories are understood without too much explanation. Many monumental experiences will elicit a strong emotional response upon recollection.

8. Epic.  Epic experiences become folklore not only among those present, but those familiar with them. Neologisms, handsigns or movements which reference but do not describe the experience may be invented and be recognizable to a large group of people for many years afterward.

9. Legendary.  The highest category of Experiential Greatness. Experiences that fall into this category, when related to others, become stories in their own right which are retold by others who are several steps removed from the original parties. The platonic ideal of a legendary experience is one that, years after having it happen to you, is relayed to you by stranger beginning with the words "I heard about this guy one time..."

This list was clearly done in fun, but it is significant to note that “Remarkable” is only in the middle of the scale.  Who knew being remarkable wasn’t enough?