Railgun.
Speaking from a person in the military whose job currently is the storing of explosive munitions...this is a horrible idea!! Not like you need specialists to stack and maintain a bunch of metal that is launched be electricity!?
Which opens the door for adventure; a new weapon arrives on the market, advanced enough to make ordinary soldiers/specialists jobs obsolete. Rather then retire quietly a group of these specialists hires a group of runners (I.E the characters) to do a little sabotage of the prototype weapon and give them a little more job security.
Breaking into a high tech military compound and subtly disabling the new super weapon before demonstration day won't be easy, but that's why their being paid a small fortune, either in cred or explosive ordinance from the back room of the supply compound.
On a non game related note I wouldn't worry too much about being out of a job any time soon, the cost of these things will keep them suitably obscure for a few more decades at least, especially with the surplus of explosive ordinance they already have stored up and ready to go.
