An image search for Wacky Packages candy turned up many ah, less-popular brands. 
Lost in memories
Tampons
Condoms
•Tijuana Bibles
•Rocks.
•Worthless hyperinflated foreign currency.
•Medication sample packs.
But of course, really, in this more safety-conscious age, there’s a responsible choice…
•Seat belts. (What the children actually do with them is their problem.)
Especially if they’re the ones that at first look like foil-wrapped chocolate coins. 
Better (worse?) still, throw one in with a bunch of actual chocolate coins. 
Packets of condiments from fast food restaurants.
Live rounds of ammunition.
Olives.
Heads, arms, or legs from Barbie dolls.
A single chicklet.
Brillo pads.
Wire nuts.
Used guitar strings.
Molded RCA plugs with the cord snipped off.
Communion wafers.
The cookie part of oreos after you’ve eaten the filling.
I always offer a fake first.
“Would you like a red potato, a white potato, or a purple potato?”
“Would you like a Brussels sprout, a carrot or an onion?” That year, I found chewed up Brussels sprout scraps on my lawn the next day. They had actually tried them! LOL!
Try to toss some of whatever you offer into some bags to entertain the parents later when the kids get home.
When the whine “Potatoes?!? Don’t you have any candy?” just say “Oh- you wanted candy? I have that, too!”
Warning, they actually like carrots, pickles, and hard boiled eggs.
So you, too, like giving out ammunition to disappointed kids, huh?
They’re not all going to be depressed-and-resigned-to-their-fate like Good ol’ Charlie Brown.
3 or 4 good squeezes of a hot glue gun into their bag.
Used socks.
So, trick for most kids, but treat for the foot fetishists?
It takes a bit of work, but is totally worth it: Carefully putting Tijuana Bible covers over the tops of Chick Tracts.
Or Chick Tract covers on Tijuana Bibles.