I'm usually too busy earning points of notoriety just for the ideas I come up with using existing gear, but I have a couple items I have pondered.
Dance Party IC
Special IC designed so that, if it strikes you enough times, it makes your physical body start dancing. This in no way impedes your ability to jack out and in no way negatively affects any aspect of your Matrix usage. Usually found accompanying Black IC in systems requiring a wired connection to hack.
Combustion Commlink
This is a commlink with a persona program that begs for help. By all appearances, two-way communication has not been enabled and a button has to be pressed to activate it. Whenever someone touches it to answer, it explodes.
Johnny Appleboom
These are specially-designed plastic explosive grenades designed to look, feel, and smell like apples. Whenever someone bites into one, it explodes.
Hot Knife
This is a flamethrower that comes standard with an underbarrel chainsaw.
Needle Grenade
This grenade is a specially-designed fragmentation grenade that is designed to unleash needles loaded with drugs or toxins instead of shrapnel.
Party Favor
A grenade that is actually a specialized alchemical item; tossing it at people causes it to summon an elemental where it strikes.
Mindfragger
This is a grenade loaded with what amounts to a very sticky glue. It also includes a small power source and a loud music player that only plays "It's A Small World After All" on endless repeat once the grenade has unleashed the glue.
Subtle Salesman
As Mindfragger, except it plays ads to encourage you to buy products from a particular company.
Mercy
This is, basically, a shotgun taser. Multiple darts at once, all wired, all unleashing electricity into the poor sap(s) you shot until you let go of the trigger or the battery runs dry.