We've all been there. This cool weapon we've just been jonsing to get. Maybe its a new submachine gun. Maybe its a silly string of death. Maybe its this vibrosword. At long last the GM says, "OK yes you can have it."
Man its just great now you've got your gizmo and life is just grand.
For the rest of the group it absolutely SUCKS when you're doing a job that's supposed to be sneaky, or low lethality and then BAM out comes the monowhip. Down goes some hapless wageslave and then you hear a player say, "I just wanted to test it out."
Let me say it for the other people that may want to but don't want to be rude. "You ~~fucking~~ what? Seriously?" If you just **have** to get your dice on for ~~fuck's~~ sake make up a 15 dice pool. Roll your little gizmo dice. Subtract its AP from the 15 dice and blam you just tested out your new thing. No job was thrown out the window, no players were saddled with Notoriety for being an amateur on a job and best of all the mission is completed and everyone is happy.
If you absolutely just have to 'test out' your weapon on a job, don't be upset when a fellow player just has to 'test out' what it feels like to called shot your character in the back of the head.