Recently, I stumbled upon Darren's Weekly Nugget 12/28/2009 on "Retaining wire values". In case you're not familiar with this feature, here's an excerpt out of LabVIEW's online help:
You can configure a VI to retain wire values so that when you create a probe on the block diagram, the probe displays the data that flowed through the wire at the last VI execution. Using probes after a VI runs is useful when the block diagram is complex and you want to debug the VI.
The ability to create Probes after a VI Runs proves useful in many cases, so be sure to use the force!