This is an good addition/replacement for built-in UnityEditor.Handles drawing methods.
Key features:
♦ Per-vertex full adjustable color, width, feather
♦ Based on Geometry Shaders fast rendering
♦ Multisampling-independent antialiased appearance
♦ Low CPU usage, designed for dynamicly updated realtime scenes
♦ Full C# and shaders code included, no dependencies
♦ Works from 5.6 and newer
♦ Builtin statistic window
♦ Lot of examples