Predecessor Builds > Revenant > Ability Haste Rev
This build focuses on having your Q up after your 4th shot on every reload to avoid the animation.
Start with Warriors crest because Rangers gives attack speed which is useless and the Glacial Colosseum passive really helps Rev with his dueling.
Mutilator gives sustain in lane and the much needed cooldowns. Viper adds more power, crit, and cooldown, and you can fully stack the corrode passive with one Q volley. 3rd can be either Infernum(heavy DoT after Q) or Tainted Blade(anti-heal for Khaimera, Rampage, Countess, etc.).
Congratulations! After those 3 ability haste items (along with a completed Icescorn Talons crest), you now have enough Ability Haste to Q after every 4 shots. Add in a Demolisher for extra penetration and crit, and finish off with Imperator for even more damage, crit, and extra damage on your crits. Now going into fights you can just throw an E, empty your clip, and Q to your hearts content. Rinse and repeat. Use your Ult with Icescorn Talons to 1v1 basically anyone and enjoy the beauty of efficiency.