I'll start by listing out the "cheesiest" Seraphon units and battalions, this is the only army I've played. It's funny because Seraphon aren't a very cheesy army, so their cheese ratings are going to be low. I'm going to rely on the rest of you for other Order cheese!
My rough definition of "cheese" is -
1) A lack of counter play. ex. a Thundertusk dealing 6 mortal wounds from 18 inches away.
2) Break the normal rules of the game. ex. Chameleon skink movement
3) Large impact for a low point cost - ex. Kurnoth Hunters or most Stormcast units
***For scale purposes consider Stormfiends a 10, Frostlord Thundertusk ~ 8.5/9, Grot Fanatics ~8/8.5, Kurnoth Hunters ~7/8
6/10 Mozzarella Balls - Chameleon Skinks - (120 points) Not the most powerful unit in terms of dmg output but definitely one of the best units in the game in terms of movement. You can't beat their ambush ability and objective snatching. Also, super fun to use!
6.5/10 Mozzarella Balls - Starseer - (160 points) Physic powers and the ability to re-roll any die, including your opponents. This ability can win you games. Learn to master the game of the dice and you can probably on average get 4 re-rolls. As a weaker hero, he is prone to assassination and still costs 160 points, but his ability is rare and very powerful.
4.5/10 Mozzarella Balls - Skink Priest with Tappings - (100 points)See below

While only a 50/50 chance, you can get rerolls for charges, runs, and saves for all units in 8 inches. No where near to broker, but in combination with other buffs and battalions, this can be very powerful.
5.5/10 Mozzarella Balls - Sarus Guard - @LordRibbit - Has shown that a 2+ armor battle-line unit with a potential of d3 damage is very powerful. You have to use a good number of these guys, 25+, to make them stick around due to mortal wounds, and they are 20 points per model. I mean, with a Priest you get a 2++ save! Without a ton of mortal wounds, your opponents will be very frustrated. Still a 1 wound model that is pretty slow, but very powerful and nothing is more cheesy than a 2++
5.5/10 Mozzarella Balls - Quicksilver Potion - A great artifact. Do you want your big monster/hero to hit first? Do you want it to be a free activation? Look no further. This is very powerful on our Carnosaurs and heroes.
@InfamousBeany
7.5/10 Mozzarella Balls - Kurnoth Hunters- 180 Points for 3, no battlefield role, Sylvaneth. Scythes or Bows are the way to go for these- you either have combat monsters with -2 rend weapons, or a unit that can shoot at artillery ranges, with artillery damage. Fantastic in both aggressive or defensive strategies, and can be dropped in army and pull their weight. I really wish there were some more efficient Sylvaneth formations to abuse these with, but alas theyeither rpovide too little benefit or are just simply too investment heavy.
9.5/10 Mozzarella Balls - Celestial Hurricanum- You know it, you love it (or hate it), it's arguably the single most versatile and splashable unnit in the game, it pumps out mortal wounds like i pump out affection for Bastiladons- the Hurricanum. 320 points, Behemoth and Leader roles, Collegiate Arcane. What can I say that hasn't already been gushed about already? It provides a flat +1 to hit to all
Order units, it increases the casting rolls of its faction by 1, it has a Kroak-esque mortal wounds spell, it can shoot
more mortal wounds up to three times a turn...phew.
We as a faction suffer from lack of ability to produce mortal wounds and some dodgy to hit roll stats- this fixes both of those. If you want to play even semi-competitively, one of these is almost a must.
@scubrat
8.5/10 Mozzarella Balls - Ripperdactyls -These guys move 14", they do a horrible amount of attacks, if you stick them in the shadowstrike starhost it's even worse, and they're only 140pts for a unit.
@ljwylde
7/10 Mozzarella Balls - (DOUBLE) BASTILADON WITH LASER - 2d6 attacks that have rend and 2 damage! A 3+ save that can easily be improved to 2+ rerolling. Ignores rend. 4+ against mortal wounds . Designed to be abused with a thunderquake/ Jade Battlemage or both!!