Tristana's Rapid Fire in conjunction with her passive will allow her to apply on-hit effects repeatedly at very high range. The MR shred from Malady will increase the damage from all her skills, since they all deal magic damage, as well as from Wit's End. Ionic Spark will trigger multiple times during a fight, especially of Tristana uses a Frozen Mallet to constantly keep targets from escaping. This will allow her to wear down the opposition in an AoE without taking return fire allowing her to finish them off with a series of Rocket Jumps.

Support Nocturne

Well, I guess now I'll answer Tank Twitch.... I'll leave my other answer here though.

Since Twitch prefers skirmishes over burst damage engages, he needs to be tanky enough to stay in the fight. Building Frozen Mallet and Ionic Spark will allow him to avoid damage while dealing damage in an AoE as well as have extra health. Ionic Spark is also good because Twitch scales very well with attack speed, allowing more procs of Deadly Venom in a shorter period.

(Don't have as much to say on that one... a bit harder.)

Support Nocturne can be a tank type support, block incoming skill shots heading at your AD carry with his shield, poke with his field of darkness thing, and an ult that can confuse the enemy while your AD carry nukes them down while they are blinded.

Tanky initiator, jungler Viktor

You're already beating on them with headbutt and knockup, might as well punch too.

Support Gangplank.

A slow, Ranged poke, an AoE slow, and AD and movespeed for all your teammates!

AP Janna(Not troll but uncommon)

Massive damage with his explosive W and his Healing ghost will make him powerful?

ADC Karma

since Siyanor didn't post the next one, It is support Khazix