First, I've been reading Jason Sholtis' compilation of The Dungeon Dozen: Random-Tables for Fantasy RPGs. "Reading" may be the wrong word, but I've definitely been picking it up and allowing photons from its pages to slam into my eyeballs.
Second, I like the way one of the zombies in Cal Moore's Shadows of Eldolan adventure randomly ends up with a pumpkin stuck on its head and keeps on fighting, since hey, what does a zombie care? I started wondering if there was another interesting zombie I could insert into a crowded market-scene, and the mook below is the result.
My guess is that the coin zombie is a necromancer's attempt to answer the age-old problem affecting most zombie attacks, which is that normal people start running away when zombies attack, and people run faster than zombies. A small expenditure of coins, an enchantment based on mortal greed, and you've got a zombie that magically convinces its targets to stick around and be eaten.
If your PCs are the type who count every coin, feel free to let them collect coins of various denominations that add up to 1d4 gp per coin zombie after the fight. If innocent bystanders and NPCs ended up getting nabbed by the jackpot or sticking around to pocket coins, subtract a few from the loot. If your PCs are the type to track down every last coin . . . [[insert GM stage-whisper]], curse the coins. They did fall out of a zombie's guts, so they were cursed to begin with.
We’re not sure where you got the idea that treasure falling out of dead monsters was a good thing, but it wasn't from this booby-trapped horror.
2nd level mook [undead]
Greedy claw +7 vs. AC—3 damage
C: Lethal jackpot +7 vs. MD (1d3 nearby enemies/bystanders)—3 ongoing psychic damage, and if target moves while taking ongoing psychic damage, it can only move to the jangling pile of coins that fell out of the zombie's crumbling body to cause this attack.
GM: If you're feeling merciful, say that a quick action to pocket some of the coins gives a +2 bonus to the save against the ongoing psychic damage. (This GM message brought to you by Jonathan-Didn't-Write-this-Monster.)
Limited use: 1/battle per coin zombie, when that coin zombie is dropped to 0 hit points.
Headshot: A critical hit against a coin zombie cancels one mook’s lethal jackpot ability that turn, though if the crit eliminates more than one coin zombie, others will still trigger their own lethal jackpots.
PD 12 HP 8 (mook)
Mook: Kill one coin zombie mook for every 8 damage you deal to the mob.