Example:

Karthus:
Passive - whenever an opponent drops below 5% health, a bolt of energy strikes all enemy champions. 3 minute cool down.

R: If karthus dies in the next 10 seconds, he enters a spirit form allowing him to continue casting spells for 7 seconds.

Poppy
Passive- this champion can only be damaged by supports
Ult- this champion cant be killed by supports

Singed always OP, ult is a passive. It's like I'm playing a champ straight out of Dota 2 and not changed by Riot.

Oh god.

Ziggs

Nuff said :l

Riven.. reforged blade all game, all day, everyday, nuff said.

Lulu:

Passive: Whenever Lulu or a nearby ally falls below 30% health, they increase in size gain 150/200/250/300/350/400/450/500/550/600 temporary max hp, knock up all nearby hostile targets and slow every enemy within 1000 range by 15/20/25/30/35/40/45/50/55/60 % for 7 seconds. 3 minute cooldown.

Ultimate: Lulu's helpful fairy friend now fires 3 missile shots whenever she attacks an enemy target (or when an ally who Pix is helping attakcs. These shots do 30/60/90(+50% AP) magic damage and can be blocked by minions and other enemies.

Lulu becomes a literal ranged ap carry. Just get lichbane, frozen mallet, and lots of ap for tons of damage on each auto attack.

Zed

Passive- Applies a Deathmark upon hitting a target with a basic attack or damaging ability. After 3 seconds the Deathmark is consumed, dealing 30% of the damage dealt to the target by Zed during the duration of the Deathmark.

R - Zed strikes a target for bonus magic damage if they are below 50% health for the next few seconds.(this is pretty lack luster)

Swain

R- When Swain deals damage 20/50/70% of it is converted into mana

Passive- When swain reaches 40% health, he transforms in this awesome bird creature that deals damage and returns to him for healing.

Kayle:

Passive: When Kayle or a nearby ally drops below 25% hp, they gain invincibility for 3 seconds.
Ult: Your attacks shred the enemies armor and magic resistance by 10% each hit stacks 4 times.

Now that's a champion I would love to play...

Teemo:

Passive: Upon standing still for 3 seconds, teemo places an explosive mushroom, dealling 20x level damage in an AoE when someone walks over it.

Ultimate: Teemo enters stealth for 4 seconds. Upon exiting stealth, he gains 30/60/90% attack speed and 10/20/30% movespeed for 6 seconds.