BetterHandles gives you more control over Bezier curves in Adobe Illustrator.
Some features are:

• Select multiple handles, and collectively move, extend, rotate, or retract them
• Extend or retract handles without changing their angles
• Edit points numerically: anchor, in handle, out handle
• Convert multiple points from corner to smooth or vice versa
• Automatically extend new handles on multiple points
• Intuitively reshape path segments, optionally constraining handle directions
• Use slow-drag to divide the cursor movement for extremely precise moves
• Equalize a point's handles
• See all the handles on a path while editing it
• Split a path at one or more points
• Delete one or more points and close the path around them
• See when the cursor is over a handle, point, or path — without having to use Smart Guides.
• And more!