Collected Company is one of Modern's new standout cards. Without it, there simply wouldn't be any Elf Company, Abzan Company, or Zoo Company. It provides card advantage, allows you to dig deeper into your deck for combo pieces, and it does it all at instant speed!
Many of the Collected Company decks also run Chord of Calling. Alongside these green instants (and sometimes Fauna Shaman as well) you often see a bunch of one-ofs, tht is, creatures that are included as a single copy only. These are typically silver bullets that wreck certain decks or cards that you don't need every game but want to have access to for specific situations. I took some time to scour through some of the Collected Company decks that were registered for Grand Prix Copenhagen to give you a rundown of the more popular tutor targets.
Some of them you will have already seen in Birthing Pod decks last year. But some are new because they are specific to novel Collected Company strategies or color combinations. And even the "old" ones have to be re-evaluated because, with Collected Company and Chord of Calling, they will more frequently enter the battlefield at instant speed, which offers some unique interactions.
Sometimes you have Viscera Seer and a bunch of creatures in play, but you can't kill your opponent on that turn. After adding Blood Artist and sacrificing your board, you may just clinch the win. Also recurring Kitchen Finks endlessly may give you about infinite life, but it doesn't exactly end the game. Blood Artist artfully does.
Eidolon of Rhetoric says no to an opponent who wants to chain an impressive amount of Desperate Rituals into a lethal Grapeshot, to an opponent who plans to cast Angel's Grace and Ad Nauseam in the same turn, and to an opponent who aims to cascade Violent Outburst into Living End.
Elvish Champion is often included in Elves decks as forestwalk can break a board stall against any other green creature deck, from Zoo to Jund. Moreover, if it comes out of a Collected Company or Chord of Calling at instant speed, the +1/+1 boost can sometimes turn an attack step which looked favorable for your opponent into a massacre.
Eternal Witness is there to rebuy Collected Company and provide even more value. And, if it enters the battlefield at instant speed, it can counter an activation of Scavenging Ooze. So keep that in mind when activating Scavenging Ooze at the end of your opponent's turn.
It has all kinds of utility: removing a blocker, breaking up metalcraft, resetting a Kitchen Finks, and so on. But the most interesting use of Flickerwisp is as a temporary Stone Rain against Amulet/Bloom! If you blink a Simic Growth Chamber, then your opponent will be forced to pick up another land, effectively setting them back one land and potentially disrupting a turn where they otherwise would play and tap Simic Growth Chamber over and over again thanks to Summer Bloom and Amulet of Vigor.
If your Collected Company opponent plays a morph against you, then your best guess should be that it's Grim Haruspex. It sees a bit of play as it offers some kind of insurance against Oblivion Stone or Damnation and synergizes nicely with Viscera Seer as well.
Hushwing Gryff puts a stop to the Splinter Twin/Pestermite combo and to an opponent who wants to gain infinite life with their Kitchen Finks. Moreover, it delays Primeval Titan and turns Snapcaster Mage into an Ambush Viper without deathtouch.
So far I've talked about using Collected Company to put creatures onto the battlefield at instant speed, presumably during your opponent's turn. But Kataki, War's Wage is an exception: If you boarded this in against an artifact-heavy deck, then that's a good reason to play Collected Company in your own main phase rather than during your opponent's turn.
Blood Moon is an important element of the Modern format as it shuts down decks that rely on Urza's Power Plant, Valakut, the Molten Pinnacle, or Slayers' Stronghold. It also punishes greedy mana-bases with too few basic lands, and it has prompted a rise in innovative sideboard answers like Chromatic Lantern. Magus of the Moon is basically the same card, except that the green instants can find it.
Together with Kitchen Finks and Viscera Seer, you can gain infinite life. Besides that, there are some rules issues to keep in mind when you are playing Inkmoth Nexus and facing a deck with Melira, Sylvok Outcast. In case Melira is already in play when Inkmoth Nexus is activated, then the "I have infect" effect in the layer is newer than the "You don't have infect" effect, so Inkmoth Nexus' damage won't affect your opponent. But if Melira enters the battlefield at instant speed after Inkmoth Nexus has already been activated, then it's the other way around, and Inkmoth Nexus will deal regular damage.
Since Wirewood Symbiote is not legal in Modern, Mirror Entity won't offer any infinite combos like people pulled off at Pro Tour Berlin in 2008. Nevertheless, in a deck that floods the board with cheap Elves and that can generate absurd amounts of mana with Elvish Archdruid and Nykthos, Shrine to Nyx, it is not difficult to set up a kill with Mirror Entity. It's like Ezuri, Renegade Leader, but it is sometimes more mana-efficient.
Fiend Hunter offers no-questions-asked removal, while Big Game Hunter is probably "tech" against decks with both Tarmogoyf and Liliana of the Veil. One way or another, this is the creature removal squad.
Pontiff has all kinds of applications, especially if it enters the battlefield at instant speed during combat. But haunt also allows for interesting timing tricks. Suppose you have Viscera Seer in play and that your opponent has four Nettle Sentinels and an Elvish Mystic. In that case, you can cast Orzhov Pontiff, giving your opponent's creatures −1/−1, and sacrifice it to Viscera Seer in response, haunting the Elvish Mystic. When the original −1/−1 ability resolves, Elvish Mystic dies, and via haunt you get to kill all the Nettle Sentinels as well.
Phyrexian Revoker can name Deceiver Exarch (even in response to Splinter Twin), Cranial Plating, Karn Liberated, Ezuri, Renegade Leader, and a variety of other cards. Just keep in mind that you cannot name any lands, so Slayers' Stronghold or Raging Ravine are out of the question.
Qasali Pridemage and Reclamation Sage allow you to take out pesky enchantments and artifacts. If your opponent casts Splinter Twin on their Pestermite, you can let it resolve, and when the opponent taps it for the copy ability, you could respond with Collected Company in the hope of hitting a Reclamation Sage to break up their combo.
Anafenza, the Foremost is great in the Abzan Company mirror match, as it stops your opponent from comboing out. It has further utility against graveyard-reliant decks like Goryo's Vengeance and Living End. Scavenging Ooze fills a similar role; additionally, it can stop Snapcaster Mage and shrink Tarmogoyf.
It deflects Splinter Twin, Lightning Bolt, Slayers' Stronghold, Rancor, Become Immense, and even the modular counter from Arcbound Ravager (although your opponent will probably choose not to use modular upon resolution in that case). One new interaction worth knowing about is against Kolaghan's Command. If your opponent wants to destroy your Cranial Plating and deal 2 damage to your Ornithopter, then you can redirect both of these effects to Spellskite. This is in contrast to Electrolyze—if Electrolyze has two targets, you can only change one of the targets to Spellskite because it can only target the same creature once. But Kolaghan's Command is a modal spell, so both instances can target Spellskite.
It is a good foil to Storm, Living End, Ad Nauseam, and other combo decks that plan to play multiple cards per turn. Maybe not as effective as Eidolon of Rhetoric, but it has wider applications as Thalia, Guardian of Thraben is pretty good at delaying spell-heavy control decks too.
Hand disruption is always valuable, especially against opponents who aim to assemble some sort of combo. The "new" thing to keep in mind is that these creatures can come down during your opponent's draw step. If Sin Collector enters the battlefield during your opponent's draw step when they have just drawn a sorcery, then that card can be taken away before they have a chance to cast it.
Well, that's it. If you were looking to round out your own Collected Company deck with some spicy one-of creatures, or if you want to get acquainted with the exotic cast of creatures that might pop out of a green instant, then hopefully this (non-exhaustive) overview, based on what I saw in the Grand Prix Copenhagen decks so far, was helpful!