In Brief: Many viewers were pleasantly suprised when they realised that after the end of Act 2 of the live action show, Sailor Moon had already used three seperate attacks! Unfortunately, Sailor Moon would only get one more attack (Moon Healing) before she became so powerful that her pure energy could be used to progress the plot.
Moon Twilight Flash deserves special attention for being the only attack in the live action Sailor Moon that had not been used in the anime or manga. It was in fact based on an attack used in an old Sailor Moon computer game, though in the game all the attack featured was Super Sailor Moon's hairclips lighting up.

Cultural: While the name of the attack is "Moon Twilight Flash!" and it does feature a lot of "moon" and "flash" you may be wondering what exactly the director of the attack was on when he/she decided to have Sailor Moon split up into three different forms of three different colours and have the spin around the screen and then merge together into Sailor Moon once more.
Well the answer is slightly silly but also interesting. You see to a non-English speaking Japanese person "twi" can sound identical to "tri" which we all know to symbolise "three". Further more, both "twi" and "tri" could easily be written the same using Japanese Katakana so while Sailor Moon is yelling "Moon Twilight Flash" those behind the scenes were most likely interpreting it as "Moon Trilight Flash".
Trilight = three lights. Or in this case, three different coloured lights.

The Attack: The attack starts with a closeup shot of the Moon Wand which is glowing a bright purple. As the glowing increases the wand shifts to the background as a the image of Sailor Moon holding the same glowing Moon Wand comes into screen. The camera pans back to reveal all of Sailor Moon's body as she screams the first two words "Moon Twilight..." and begins to spin around at an amazing speed. As she's spinning her body splits up into three seperate colour spectrums, pink blue and white which spin around the screen indivually before joining together for Sailor Moon to aim her wand at the screen and yell "...Flash!".
Pink and purple fireworks fire from the Moon Wand's tip.