Here are some of mine:
Jumpjets: take any colored jetpack piece for minifigs and place it on the battlefield. When a unit puts it on, they gain the ability to "jump" up to 10 inches vertically each turn in addition to normal movement. Combine the two for awesome maneuvers.
Universal Remote: Take a walkie talkie piece and attach a flat painted 1x2. Roll a d6 to use a universal remote (counts as attack phase). A roll of 2, 3, 4, or 5 let's the unit holding the remote take control of any electrical or mechanical device within an 8" radius for that turn.
A roll of 6 gives unit permanent control over the device until the unit dies or the remote is destroyed.
A roll of 1 destroys the remote and does damage to the unit. (1d6?)
Fun Idea 1: Unit comes in range of enemy machine gun turret, unit uses universal remote, the gun turret spins around and fires at enemy troops.
Fun Idea 2: Unit takes control of nearby enemy car using universal remote. Windows roll up, doors lock, windshield wipers go haywire, the Macarena plays over the sound system, car is sent careening into a wall at 60 mph.
+
or
Portable Portal (Portalble for short): Designated color of suitcase. Units holding portable portals can send handheld objects and weapons to any other portable portal on the battlefield. (Portable Portals have been known to reject objects such as flags in CTF games.)
Fun Idea 1: Enemy unit is seen carrying a Portable Portal. Take your own Portable Portal and send them a live grenade just as it explodes.
Fun Idea 2: Have a squad member carry a portable portal device and keep another in your base to easily resupply them with weapons and armor.
Share your ideas and experiences!





+ a grey nozzle of some kind (for whatever reason I couldn't find a picture of one on Bricklink) = Fire Extinguisher.