Infinity Shift from Dark Matter core is beastly at level 3. Not only are you invincable while using it, you teleport around without having to close in on enemies. Combine that with life steal, and it is almost instant full life when used. Also can take most bosses down by half HP with 1 use.
100+ Retail Games_100%
100,000 GS (9/12/09)
200,000 GS (2/2/2014) (I blame MMOs)