I've been poking around in the 'similar items' dictionary, and have found a surprising number of mostly-useless, but still rather interesting, DC items that simply aren't listed in the Batcomputer.

What I've got so far:
- Aerodiscs (held item, allows flight... should be like a hoverboard, but oh well)
- Lasso of Truth (acts as normal lasso)
- Books of Magic (held item, does nothing)
- Reduso (held item, does nothing)
- Razor Boomerang (acts as normal boomerang)
- Collapsible Boomerang (acts as normal boomerang)
- Worlogog (held item, does nothing)
- Tantu Totem (neck slot item, does nothing)
- Jewel Kryptonite (acts as normal Kryptonite)
- Anti Kryptonite (unsure)
- Beefeater's Battle Rod (held weapon, not sure of strength)
- Pied Piper's Flute (held item, does nothing)
- Doctor Mid-Nite's Infrared Goggles (face slot item, does nothing)
- Doctor Mid-Nite's Ultrasonic Lenses (face slot item, does nothing)
- Helm of Nabu (head slot item, does nothing)
- Green Arrow's Trick Arrows (quiver that, when interacted with, randomly spawns a trick arrow)
- ** Trick Arrows all follow the naming formula of "Green Arrow's * Arrow", with the wildcard being either Combat (normal arrow), Flash (acts as normal arrow), Bolo (acts as normal arrow), Net (acts as normal arrow), Cryonic (briefly freezes things), Explosive (explodes), Boxing Glove (long-distance punch), Tear Gas (creates short-lived cloud of smoke that gives 'Crying' adjective to things). All arrows are thrown weapons.
- Joker Fish (fish, moves EXTREMELY erratically)
- Hard Light Construct (offers choice of Hand, Bat, Shield, Cage or [mini]Gun. All act like their normal counterparts do when given the 'Living' adjective)
- Utility Belt (belt slot item, does nothing)
- Bat Bolo (does nothing)
- Acid Capsule (held item, can be thrown, does nothing)
- Shark Repellant (held weapon, not sure of strength)
- Batgrenade (acts as normal grenade)
- Remote Control Batarang (held item, does nothing)
- Batarang Remote (held item, does nothing)
- Bat Cowl (head slot item, does nothing)
- Radio Bat Cowl (head slot item, does nothing)
- Lab (Batman's) (solid object, gives the 'atom' speech bubble when interacted with)
- Batcomputer (solid object, beeps when turned on)
- Batmonitor (solid object, does nothing)

Has anyone else been able to find others?