Not wanting to be left out of all the fun, here's my contribution for Tim Hall's OTN Appreciation Day event...
For those of us that came from an Oracle Application Server (iAS/OC4J) background, and with maybe a particular OCD-style bent for automation, I think the the biggest discovery in WebLogic Server was WLST, or WebLogic Scripting Tool. This lets you access the underlying JMX management objects that control every facet of WebLogic via an easy to use tool Python (or, rather Jython, the java variant). Python itself is fairly popular these days but nearly 10 years ago it was a bit of a novelty for me but gave me lots more scripting flexibility and control compared to traditional shell script.
Anyway, for a couple of years I was touting a presentation called "WLST - WebLogic's Swiss Army Knife!" extolling the tool's virtues!
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