Homura and her hammer space shield. Seems that Gen wasn't really fond giving her only this as weapon, but after seeing the storyboards it seems that he liked the whole pulling machine guns out of nowhere dynamic. The producers also liked it.
More on the shield:
ほむらの盾に見えている武器が砂時計で、その砂の流れを遮断することで 時間をとめているんです。で、砂時計の上部分の砂が全部なくなった時点で ひっくり返すと１か月分の時間が戻る。それまでは止める事しかできない。 つまり、砂時計の１か月分の砂をやりくりする能力がほむらの特殊能力なんです。 まき戻った時間は…そこが主題の作品ではないので厳密には考えていませんが 世界は平行して分岐しているのかな、と思っています。
Q - Could you elaborate a bit more on the power of Homura?
Urobuchi - The weapon that looks like Homura's shield is actually a sand timer. When the flow of the sand is blocked, time is stopped. And when there is no sand on the upper part of the sand timer and then the timer is reverted, one month's worth of time is turned back. But before that stage is reached, only time stopping is possible. This means the special power of Homura is the ability to manipulate one month's time's worth of sand in the sand timer. As for the time passed and then turned back, since it was not the focus in this work I did not think it through very thoroughly. I think you can say that the world split up and became parallel worlds there.