Ami is a very intelligent 14 year old girl. She loves to study and is an over achiever. She's taking special computer classes and a "cram" school for college, and her usual test scores aren't anything below 99%. Strangely, she's always saying weird unintelligent things to make the other Senshi look at her oddly, causing her to blush just a bit. As a Sailor Senshi her she is the one who analyzes a situation. Most of her attacks aren't what you exactly call offensive attacks, but she uses her defensive attacks to keep the villain from causing any harm to the rest of the Senshi.

Mercury Power
Ami says this to turn into Sailor Mercury
Mercury Star Power
Ami says this to turn into Sailor Mercury, later in the series.
Mercury Bubble Blast
Sailor Mercury's main attack, when she says this she releases foam bubbles which create a sort of fog that blinds her enemies.
Mercury Ice Bubbles Freeze
This attack is basically just like Mercury Bubble Blast, except they're ice bubbles..
Mercury Ice Storm Splash
When Sailor Mercury says this, she creates an ice storm which freezes everything around her.
Mercury's VR visor
An extremely useful weapon, Mercury presses her earring and these special blue goggles come down from her tiara, with it she can see the evil in people's hearts, and other important things that couldn't normally be seen.
Mercury's Pocket Computer
Another nifty gadget that Mercury has, she uses this computer to analyze situations and other things like that.