Consider (have):
Soul's Fire - Fling effect that doesn't sacrifice
** Pongify - Cheap removal
Thieving Skydiver - Steal a Sol Ring
Slip out the Back
Molten Birth - Can get a lot of tokens potentially, but it's mana intensive and quite low impact
Artful Dodge - Unblockable one-shot that can be used twice
Wizard Class - No max hand size is nice, but probably not going to be relevant most of the time, and getting to level 3 is very expensive
Loxodon Warhammer - Trample and lifelink
Crash Through - Cantrip that lets Okaun trample
Helm of the Host - More Okauns
The Royal Scions - Can give Okaun trample, or loot away cards, but I can't really protect them if people want to just attack it down
Valakut Awakening - Wheel away the stuff I don't need, or be a land in an emergency
Aqueous Form - Permanent unblockable and no protection is likely to make Okaun an attractive target. One-shots from hand might be better
Kediss - Might be hard to connect with Okaun, and I won't know if he will get huge before combat, at which point it's too late to surprise with this
Temur Battle Rage - Can make a semi-lethal Okaun VERY lethal, but I'd probably rather just make him unblockable
Footfall Crater - Hasty Okaun
Boompile - Sweeper with flipping, but a bit too unreliable and when I can manipulate or get value from the flip, I don't really want to blow everything up probably
Two-Headed Giant - I don't think the flips have a winner, but it does let me flip two coins
Prowler's Helm - More unblockable equipment
Gravitic Punch - Double Fling without having to sac, but a bit high CMC
Thassa - Smuggle Okaun
Goblin Welder - Another way to get back the Thumb
Thassa's Oracle - Draw my deck with Zndrsplt + Efreet then win

Maybes that are in other decks:
Trailblazer's Boots - Unblockable eq for Okaun
Shadowspear - Trample and lifelink
Key to the City - Can use this instant speed only when Okaun actually is big enough to matter (or to smuggle a Ragavan when people start getting blockers), or just to dig
Strionic Resonator - Copy the attack trigger

Consider (from high power):
Imperial Recruiter, Drift of Phantasms - Tutors
Ragavan - Early Ragavan is great for ramp, but the board quickly gets to a point where he can't do anything. Having ways to give unblockable helps, though

Consider (don't have):
* $$$$ Copy Artifact - An extra thumb
$ Puppet's Verdict - Sweeper
$ Fighting Chance - Potentially a bunch of flips
$$ Karplusan Minotaur - A lot of flips and potentially removal, but it's risky
$$ Seize the Day - Extra combats
Thud - Cheap Fling effect
Goblin Traprunner - Probably needs to be unblockable to attack safely, but gives me three flips on attack with the possibility of some tokens as upside
Triskaidekaphile - No max hand size, mana sink and alternate wincon
Distortion Strike - Cheap, one-shot smuggling that works two turns in a row
Desperate Gambit - Flips a coin for R, and can double the damage of Okaun, but risks fogging
Goblin Bomb - Flip a coin every turn and cash in for 20 face damage later
Goblin Archaeologist - Flip a coin and maybe destroy an artifact each round
Chaotic Strike, Aleatory - Cheap cantrips that flip a coin and give a minor buff
Shadow Rift - Smuggle Okaun and cantrip

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Considered cuts:
Match of Swirling Mists
Ral Zarek - Getting to the ult is probably going to be very hard, but should win the game
Mirror March - Magical Christmas land gives me a bunch of Dockside copies or Phantasmal Images, but this is very high CMC and I don't play a ton of creatures
Malevolent Hermit
Brain Freeze + Breach - cEDH cards