When you have magic or magic abilities/powers, you have to imagine the grossest thing someone can do with it. Not because they WILL do it, it is your character after all, but the reader may wonder why they didn't use it during a time of desperation when the bad guy had his loved ones at their mercy, etc.
Have you ever thought something like this while reading about a character with a nice little utilitarian magic ability?
"Oh, I can only create an ounce of water at a time, but I can create it - IN
YOUR EYEBALL! muahahah!"
Is that gross? Not gross as in "ewww sick!" but gross as in that's way more
deadly/harmful than you had intended. Solve the problem in a simple and logical
manner. Perhaps they can only make an ounce of water in free space, in a cup,
over the palm of their hand or over someones head, perhaps in their mouth if
it's open (minor choking hazard meh) and the problem is solved. Again, you don't
have to pad it down to child safety regulations, but you may want a reason why
the character doesn't just unleash his seemingly utilitarian magic ability in a
method that would give the villain a very bad day--and in some cases, this works
very well in line with the story.
The guy that can shape stone: can he turn the pebbles under someones feet
into nail-like shapes? Can he flatten rocks at the base of a cliff until he
creates an avalanche? Perhaps he can make hand and footholds in the same cliff
and scamper right up it...bad guy chases him and poof he makes the holes go away
making bad guy fall to his death. Is it gross or just very effective in the
right situations? As the writer, explore his ability and what YOU want it to do,
think of logical limits and where the line of power is for your story.
A simple fix if its gross- he has to touch the rock he is shaping, where he
is shaping it. Now he can carry a bag of rocks and turn them into barbed
missiles one at a time and throw them...or can he shape a bigger stone into a
shield, block the bad guy's sword with it and shape it around the bad guys sword
and arm to trap him while he pokes him in the eye with a long thin lance of a
stone that he makes longer and thinner to penetrate deeper...OK so now he can
only shape stone he is touching slooowwwly, or he has to say something very
specific out-loud so its a dead giveaway that he is about to do something.
And soon an actual working magic system begins to take shape, with checks and
balances and abilities that can still be unique and colorful.
There is a great anime called "Read or Die" where three characters can only
manipulate paper, and they each do so in different forms. It is an awesome
exploration on magical material manipulation.
The main thing is to really think about what the capabilities of your magic
are and how they could be misused and overused. It is also fun to explore how
your characters magic may grow with them...does it gain power with practice?
Does the longer the character goes without using it make it stronger, like he
was building up energy over time?