Oddest thing I've used was bottle caps. There were some of these little flavored water things kinda like Kool-aid. The tops looked like alien ships so that is what they became. I also used normal Coke bottle caps. I've used a Transformers Dragon (Megatron) as a Dragon.
Our party ran across a dire bear and all we had handy was a pack of those plastic paintable carebears.. Luckily, someone had brought their new camera to show off that night!
As someone who has never used an actual miniture in my life -
Coins.
Done the paper mini thing (like SJG carboard minis) that I printed myself.
Dice.
Taht is about it. We only use the map for location and never worry about anything else... no one in the group has the time or inclination to paint pewter minis, or the desire to buy the collectable ones. ... although I have a group of Storm Troopers and Clone Troopers on the shelf that holds my Star Wars novels and comics.
A guy in our group once listed the height and weight of his warrior as 6'7", 170lbs. He wore full plate.
I found some of that styrofoam they use for plant arangements (green & hard instead of soft & white), cut it into a hexagonal shape, and shoved a needle in it.
He protested that he miswrote the PC's weight, and it was supposed to be 270lbs...but we always made him use the needle.
(That campaign is over now, but the "mini" remains.)
In an adventure I ran (written up in this thread here - http://www.enworld.org/showthread.php?t=154448 ) I used some of those giant rubber spiders. I also have a big bag full of various animals. I try to get a picture of them soon.
Not much 'goofy' for use in RPGs, but in Warhammer... I used to have a cheap plastic Kermit the Frog seated, wearing a crown and holding a scepter. Kermit the Slann struck terror into the hearts of his foes with his mighty battle cry of 'Hi ho!'
If I still had the figure (which disappeared years ago) I would still use it...
The Auld Grump, who only had Lizardmen because they came in the box set.