4. Individual Powers
One of the things that attracted me to Charmed, in the first place, was the concept of individual power. Each of the three sisters has their own classification of power, in addition to their collective Power of Three. Prue and Paige powers were 'movement' related; Piper could manipulate molecular structure and Phoebe had abilities relating to foresight, feeling and perception. Whilst most witches on television can, pretty much, make anything happen in a wand-waving (Harry Potter), finger-pointing (Sabrina) or nose-wiggling (Bewitched) kind of way, Charmed had clear boundaries of what a witch was, what she could and couldn't do. It is always more interesting when a television character has a limitation, a weakness to overcome. This was especially important on Charmed, given that they were titled 'the most powerful witches alive', as it was more interesting to see the sisters confront something stronger than themselves, especially individually. There was very clear demarcation about what each sister was capable of and it ensured, for much of the series, that they would always need their sisterhood to combat their Evil foes, with no sister transcending the collective. I think this is what made the Halliwells the kind of TV witch that had never been shown before - a witch with responsibility. Another dimension enjoyed by fans of the show (and me) was that the sisters powers grew throughout the series, to the point where they developed new ones (as discussed above).
Prue, the oldest sister, to begins with, had the power of telekinesis (a time-honoured ability in popular fiction) which she could only channel through the eyes in Season One. By the end of her last season (Season Three) she could she use this power through her hands and could, also, use it to perform superhuman acrobatics and martial arts manoeuvres ('Primose Empath', 'Wrestling with Demons', Season Three). During Season Two, she had also developed the power of astral projection ('Ms Hellfire'): the 'movement' of the soul from the body into a second tangible body - basically a cross between teleportation and cloning. Piper, the middle sister, seemed to be able to 'freeze time', initially until it was learned she actually had control over the speed of molecules (bit of a reach, but they still got away with it). Therefore it was very much a surprise when she gained the ability to 'blow things up' ('Exit Strategy', Season Two). Initially it was uncontrollable and very violent. However, once she gained control over both her powers she became one of the most powerful being in the Charmedverse, a role very much needed after the death of Prue ('All Hell Breaks Loose', Season Three). One of her most impressive feats was learning to selectively 'freeze' demons, meaning she could freeze their bodies and leave their heads unfroze, making it much easier to threaten and interrogate enemies ('Sleuthing with the Enemy', Season Three, 'Once in a Blue Moon', Season Seven).
Phoebe - the original 'baby' of the family - had the power of premonition: to see visions of the past and future. Her power advancement went a bit off course, however, when she gained the power to levitate in the Season Three premiere ('The Honeymoon's Over'). However, in the Season Six premiere ('Vallhalley of the Dolls') she was given the power of empathy; to feel, and manipulate the emotions of others; which was much more appropriate.
Paige, the secret fourth sister discovered after Prue's death, was half-Whitelighter (a race of guardian angels) and, therefore, had hybrid powers which, to be honest, kind of sent the power rules a bit haywire. She could 'call' objects to her hands teleport or 'orb' ('Charmed Again') shapeshift ('House Call', Season Five) and heal open wounds ('Payback's a Witch', Season Eight). Her powers were probably the least thought out and made her a bit too powerful towards the end of the series. Nevertheless, their powers stayed pretty faithful to the advancement concept and each of the Halliwell witches honed their individual abilities before developing a new one, something which, interestingly, had never been tried before on a tv series.