I think between Jack's katana, Megaman's repulsor canon, and Iron Spider's waldoes (the spider leg things), Sam's got some very sticky fingers. There's nothing wrong with borrowing things, as long as she returns them.
At least we know those blasts are doing some good, since we know Blossom is taking a little damage from deflecting each. But because Phineas & Ferb shows all too clearly the consequences of a misplaced shot, I wonder where the blasts will end up next.
I also think it's strange how much Buttercup is holding back now. Perhaps now that the initial thrill of the fight has worn off, she's starting to internalize some of Jack-sensei's teachings. If she is, not only will she be the 'strongest' Powerpuff, but also highly disciplined and focused. Mind you, we already got a glimpse at high focus with Blossom's Holmesvision. Maybe Buttercup's focus will more closely resembled that of Kato, from The Green Hornet, where it highlights what to hit and how and when.