As yet another season of League of Legends begins, yet another set of champions become strong according to the new environment of the game. Hopefully in this tierlist, we get to see who's fotm right now and who's generally bad when it comes to the ADCs of the game. My initial tierlist will be based on my personal opinions, but hopefully I could get back to this post with some people adding ot the discussion for a more comprehensive analysis. That said here's how I see the game, as of patch 5.1, from the ADC's PoV:

Tier 1: Corki, Graves, Caitlyn

Tier 2: Ezreal, Lucian, Draven, Vayne, Jinx, 

Tier 3: Kog'maw, Tristana (pre-rework), Sivir, Twitch, Miss Fortune

Tier 4: Ashe, Kalista, Varus 

Tier 5: Urgot, Quinn, Jayce, Teemo, Twisted Fate, etc.

The reasoning behind my personal opinion is what's currently needed in the ADC position, which are namely movement and raw damage output, sadly putting the more utility-based ADCs at a lower tier than the others. This puts the high-damage, high safety champions higher up on the list. Aside from this, I also looked towards the most recent patch notes to see how each ADC has been progressing throughout the latter S4 and early S5. Hypercarries have also dropped a few notches as the new season is more focused on the midgame teamfights.

Other (minor) sources of influence in my decisions are the most frequently banned/picked champs in competitive and challenger, and the most popular overall champions.

Edits (aside from actual tier movements):

Added in Sivir (I haven't seen one in so long I forgot, sorry); 

Added a Tier 5 for unconventional picks (not saying that these are necessarily bad, these are just less consistent with other ADC picks, as they're usually played elsewhere)