My son has been into Pokemon for quite a while; sometimes it’s all he will talk about. In an effort to change the subject, I told him about the Topps Wacky Packages I collected with equal fervor back in the mid-seventies.
I also collected rocks and minerals (I still do).
What did you collect when you were growing up?
In no particular order:
Hot Wheels
foreign coins and stamps
neuroses (for later use)
I collected badges/pins
I collected pigs. I love those pink lil things. Then I went on to unique tea pots, I have about 70 or so of those and now I collect angels and have about 50 at this point.
Turtles, stuffed, and knick-knacky types.
Books, old school books specifically.
and… (y’all are going to think I’m nuts)
for a while, bags. Mom would get a neat or pretty bag from a store she shopped at (think apparell stores) and I’d fold it up and smooth it out and stick them in a box. Why? Who knows. One of my efforts as a child to perfect a world out of control when my parents were divorcing. Comes out in weird ways, eh?
GI Joe action figures (not the big dolls, the little 2" tall ones)
Masters of the Universe.
Comic books (which I still collect)
garbage…
Bottle caps and matchbook covers.
Business cards (I had about 5,000 at one point), keychains, matchbox cars, and toy banks. I also collected baseball cards, but that was only because of peer pressure 
Well, it wasn’t me (really) but my best friend’s little brother had a booger collection that was on the wall by his bed. It was, and I’m not lying here, 3 feet in diameter. Quite a collection, I’d say
Bazooka Joe comics from the gum. No clue as to why. Maybe for the fortunes on them…I was a weird kid.
Because if you sent in 300,000 with $4.95 S/H, you could get joke “hot pepper” gum?
Postcards
Pennants
Buttons/pins/badges (I actually kept my faves on my beanie made from one of dad’s old fedoras)
Rocks - I got a “Tumble Stones” kit for Christmas one year, and was constantly in the garage polishing rocks. My Mom found some of my old rocks and gave them to me for Christmas. It was like seeing old friends.
Rocks, bottle caps, comic books, slugs, stamps, corks, coins, caterpillars, Happy Meal toys, matchbooks, Mad magazines, corks, Cracked magazines, Matchbox cars, the occasional Sick or Crazy magazine and those little soaps from hotels.
Oh and yeah, Wacky Packages were super! Though I don’t think my grandpa appreciated us sticking them all over the interior of his Buick.
Ha ha ha. I had a whole box of the dumb things. Kind of like saving up S&H Green stamps, huh?
The usual things:
Bottle caps
Marbles
Bugs (much to my Mother’s annoyance)
Dirt (again to my Mother’s annoyance)
Shells
Pretty stones
Stray pennies
Comic books by the ton
Assorted plastic model parts
Basically anything which I could stuff into the pockets of my jeans.
Snake skins (my Mother was used to me by then)
Small, bleached out rodent bones found in the woods
Smooth bits of sea glass.
Rocks
Frogs
Marbles
Stamps
Just about anything.
Things I collected:
Stamps
Hot Wheels (mom threw these out later $#%^&@!*!!!)
Topps and Fleer Baseball Cards (used to flip them too and trade)
Praying Mantises (Kept them in the back yard and in shoe boxes until mom beat me silly to get rid of them…)
Worms (for stuffing down girls shirts in Kindergarten, didn’t last long…)
Spiders (i like spiders)
Things I lost as I got older:
Freckles
Sanity
Virginity
All of the above eventually…
Cicada shells
Roly Polies, which were always dying on me!
bottle caps, until we moved closer to my mom’s relatives and my grandmother let me know that another cousin was collecting bottle caps already, so no one would help me collect them. My mom convinced me to switch to matchbooks, which I never really liked.
In order from when I was very young to teenager:
Bottle caps (very smelly; Mom threw away)
Marbles (recently rediscovered, my daughter’s got 'em now)
Hockey cards (sold 'em to pay for my wedding)
Comics (sold 'em to buy my first car…STUPID Elkman!!)
Stamps (traded for coins)
Coins (to this day)