League Of Legends

Caitlyn
The zone control marksmen (traps are on a charge system now)
New play feel with headshot combos (trap and E trigger a guaranteed headshot on the target)

Miss Fortune
The wombo combo marksmen (ult scaling way better, can crit)
New play feel with impure shots replaced with "love tap" new passive that gives bonus damage when swapping targets (this works well with Q)

Kog'Maw
The true glass cannon hyper carry (tons of dmg needs protection)
W now doubles ALL attack speed and allows him to break the attack speed cap (but ad is lowered to 60%)

Corki
Magic damage marksmen -> passive now does big magic damage instead of true and all spells now do magic damage
New mechanic: Special Delivery -> every ~5m in the game corki gets a special set of bombs in his base that allow him to cast a super mega W with much bigger range and impact

Quinn
The map mobility/roaming marksmen
R reworked as a utility focused spell -> 0 cooldown and gives quinn crazy out of combat speed to quickly move around the map, not used for assassination anymore

Graves
We finally made his shotgun a shotgun -> up close burst damage marksmen
Basic attacks fire multiple buckshots in a cone -> more damage up clost
Q reworked to synergize better with the new basic attacks"

Infinity Edge is slightly weaker now (little less AD), we shifted power elsewhere so it's less automatic and so that we could add cooler things to the Marksman space.

Essence Reaver scales its CDR off of your critical strike chance so that it works as a big core item (think IE space). It can now give upwards of +30% CDR.

Phantom Dancer does stuff other than just be straight up damage. Bonus movement speed while near your opponents and you take last damage from the last champion you hit. Isolate and kill people, basically.

Rapid Firecannon charges up like Shiv, but when charged instead of prepping you for the thunder, increases your attack range and gives you a fiery hit at the end.

Shiv does even more damage versus minions. It's specialized further into being the bursty clearing tool.

Hurricane now crits and the bolts crit. Also movement speed. It's in the PD / Shiv space now, so it should be an option for more Marksman.

Executioner's Calling is back, but it's a bit different and cheaper. Also it's a component item. It builds into something new.

Last Whisper is now a component item. It builds into new things.
There's something called Giant Slayer. It hurts health dudes.

Merc scimitar has Lifesteal, you should feel comfortable taking it over BT.

Death's Dance exist. It has something like Lifesteal but better. Also it "delays" damage.
And tons of changes all over the place. This is just some of the marks targeted ones.