Leaving aside the philosophical question of "what is an item?" (if I scratched my table it would remove some atoms, still a table, do it enough and it falls over and is no longer a table even if 80% of what was my table is still there and it also depends where I scratch).
You basically break thermodynamics with this one so that -- can either instantly heat something or instantly cool it, that or you are creating energy or destroying it (so still breaking thermodynamics). You might even be able to have some fun with atomic physics if you make things larger than atoms can hold or small enough that they become their own little black hole (ones with little mass tend to blink out of existence fairly quickly) -- oh no more nuclear waste (not that you need black hole levels for that -- see how explosive compression nuclear bombs work, short version closer together = more activity = shorter half life or indeed potentially more power from the same substance).
Depending upon how atomic physics works in this you also could wind up making perfect shielding for radiation, something your oxygen will never escape from (to say nothing of silly mass of it in reserve and potentially able to be made from other atoms) and with that, possibly plus a black hole drive too, you have space travel sorted.
Computers would be the same in that you could miniaturise things, or fix them.
You could blow things up from atomic size, shape them perfectly and shrink them back down to do incredible things.
Even more basic then depending upon how mass works in this then you also change logistics overnight -- mass and volume tending to be the key drivers.
So yeah it is a crazy broken power.
