Since I've been playing with OpenHAB I've mostly been collecting data, as that's easy.    But recently been adding some funkier items.  So less about the technology, but some of the interesting things you've done - unless an integration is the interesting thing.

Paradox Alarm

I have two methods of accessing this, one is a python script, but recently been changing this to a windows service which not only gives me states of PIR devices, but I can control an Output (PGM) or the arm/disarm state.

Lighting rules.

I have a few zwave relays on various outside lights.  I also have a weather item for sunrise/sunset which sets a day/night switch.

Using the alarm - ie has house been disarmed/armed, and is it night time - two sets of outside lights come on as it means: a I'm leaving for work at 6:20am (in winter it was dark), or b, we're just getting home at night.  These two lights are turned on for 15 mins.

Another one for some carport lights, accessible via a spare room (that has a reed switch on the door), say if night time, and door opened, turn on these lights for 5 mins.

That 2nd rule for the car port, while great for at home, and the alarm great if we're all out, doesn't work if the house is not armed, and say my wife is out.  So using the unifi binding (which detects if a device is online/offline depending if it's attached to an AP), then if the user comes online (from off) and it's night time, then turn on the same sets of lights.

Fan control

A bit of cool stuff (I think) and a rule, a mosfet switch attached to a raspberry pi, then turns on two 12v 120mm computer fans - something a raspberry pi couldn't do off it's 5v or 3v GPIO ports.  Coupled to a MQTT topic then a temperature sensor (on the same pi) updates the temperature, and if above a threshold turns on the fan.

Battery devices check

Battery devices annoy me, but I've got some.  So I added a check on the batter level, it then sends a message via an item - coupled to mqtt wich is picked up my mqttwarn (hat tip @sumnerboy for the item configuration)

Kid Youbtube monitor

We're not too keen on the 8yo having unrestricted access to youtube.  So in the weekend when his cousin was around, and they were mucking about in it despite my request not to, I figured out the Roku API calls to get the current roku channel.  When I see it's youtube, I can hit the home button via another API call (bwhahahahahaah TEH POWER!!!!).  I need to figure out the same with the apple tv...but I actually have all the parts to do this.

I think that'll do.  If nothing else, someone may find these useful and want to duplicate.  Happy to post how I did any of them, or someone can mention their own which may tickle my fancy.