Riot Games released the Patch 4.5 notes for League of Legends today, which detailed big changes to Rengar, Gragas, and a new item in Feral Flare.
First, there are changes to Rengar's kit across the board. The goal is to add depth to his gameplay and allow him to participate meaningfully in team fights. The first change is to his passive, Unseen Predator. Instead of Rengar becoming visible mid-leap, he'll now become visible at the beginning of the leap. This will probably hurt his ganking in a minor way, but they'll still be effective. His Q, Savagery, had its cooldown reduced, but in exchange, the base damage has been lowered at each rank, with the AD ration increasing each rank. Now, he'll only get an attack speed buff on Empowered Savagery. Battle Roar had it's cooldown changed to a flat 12 seconds at all ranks. The bonus armor and magic resistance has been nerfed, but new to the ability is: Bonus armor and magic resistance increases by 50% per enemy champion or large monster hit (no cap).
Bola Strike is no longer a targeted ability, it's now a skillshot. The cooldown is 10 seconds at all ranks, but the range and slow has increased dramatically. The last big change is to Bonetooth Necklace. Instead of taking an item slot, it is now a Trinket. You'll have to make the choice over whether to go more offensive with Bonetooth Necklace or get vision from your vision trinkets.
The changes to Gragas increased the strength of his close-combat abilities and makes him less of a sniper, since he was intended to get into the thick of things and be a brawler. His sustainability also takes a minor hit.
His passive, Happy Hour, now restores 4% max health instantly instead of 2% max health over 4 seconds. Barrel Roll had its base damage and ability power ratio lowered. Meanwhile, Drunken Rage gets its cooldown lowered significantly, adding a sheen-type next attack damage buff to it, and giving Gragas the ability to move at 80% speed while drinking. Body Slam had its cooldown increased slightly, the but mana cost is lowered and the base damage and ability power ratio is raised.
Feral Flare is a new jungle item that focuses on late-game farming in the jungle at the expense of meaningful early to mid-game power. Feral Flare upgrades from Wriggle's Lantern after killing 25 large monsters. It gives +15 attack damage, +35% attack speed, the ward casting range is greatly increased (yes, it still grants a stealth ward), it gives +30% gold from monster kills, and basic attacks deal 100 damage (reduced by 67% against champions) and heal 10 health on hit. Kills assists and large monster kills increase the damage by 3 and heal by 1.
There's a ton more changes, including kit changes, buffs to Miss Fortune and nerfs to Heimerdinger, which you can read about HEREin the full patch notes.