Well, it's hard to imagine a scenario where a microscopic blackhole won't instakill its target within the local vicinity - however, there might be something fun to be refined out of it. What do people think about a warhead type as a minor faction bonus?
I can.
"It's called 'real life.'"
The smaller a black hole, the less mass it has, and the shorter it's lifetime. A 100,000kg blackhole would last 0.08 seconds and have a radius of 1.484852 * 10^-22 meters (about the size of a quark). The odds of it actually gobbling down any mater at all would be vanishingly small (ergo doesn't instakill anything). And of course, moving it about would be just as difficult as moving about anything else that weighs 100,000kg (except it would also be the size of quark, so you'd have to use magnetic fields rather than a stick to push it).
(If you want "microscopic" as in "the size of a cell, visible under a microscope" you're starting to talk about "an object with the mas of a small moon." A black hole with a radius of 0.000001 would be half as massive as Charon, Pluto's largest moon. Which would probably only instant-kill via blunt force trauma and require an insane amount of energy to push about).