Query builders- sample value list

One of my clients asked me if it would be possible to get list of values for an attribute when using the Query Builder.  I initially thought this wasn't necessary because the boxes are auto-complete in nature.  His response was that users don't always know what type of data (string, numeric, etc.) or what values may be present to look for.  A complete list would be nice, but at least a sample could be very helpful for less experienced users in executing queries.