useless gift ideas

[mmswm]

Metal Slinky

[oz diva]

Once I found an extremely naughty X rated, join the dots book. Then I just had to find someone to give it to. ( I tried some out, after photocopying the pages and it was very naughty).

[amandaelizabeth]

An inflatable dart board

[bonyk]

fab.com has a lot of useless, but interesting stuff.

[AmethystAnne]

A jigsaw puzzle from the toy section of the local dollar store. [I bought 4 for myself: row houses in Germany, colorful gum balls, tulip field in the Netherlands, a flower patch of zinnias.]

I'll repeat the suggestion of a metal Slinky.

coloring books and a box of Crayola crayons (the 64 pack with the cool crayon sharpener on the back of the box)

Find-A-Word books and a Bic pen

giant(!) eraser and a pack of pencils - in the traditional yellow or in neon colors

[Outdoor Girl]

Once I found an extremely naughty X rated, join the dots book. Then I just had to find someone to give it to. ( I tried some out, after photocopying the pages and it was very naughty).

Oh, man.  That would be perfect for a cousin of mine!  I might have to check some of the local Adult stores.

[BabyMama]

Last year I put together a box of stuff leftover from the previous owners of the house. There were Spacebags in the closet, so I tossed them in. Apparently the person who got them LOVED them.

[The Wild One, Forever]

...

One year I was late looking for calendars and the only ones left in the store were Jonas Brothers.

How sad that must have been for the Jonas Brothers!   

Those fifteen minutes go by fast.

Some of the best white elephant gifts I have seen are silly holiday decorations, especially those with animation.  At a work party Yankee Swap one year, the gift everyone wanted was a singing "sultry snowlady."  I also seem to recall one of those mounted fake wall fish that sang some holiday song, and that was hilarious, too.

[Redneck Gravy]

any hideous painting on black velvet

vcr tapes - bonus if you can score beta instead of vhs

[Bijou]

The local dollar store sells pairs of "fuzzy socks" for $1.  Except they are striped and in neon colors like yellow and green, pink and green, etc.  Nobody in their right mind would want to wear them because they're scratchy due to the little strip of "silver" on the ends of the fringed yarn.  They're also a bit too small for most adults, and a bit too large for most kids.  Perfect useless present.   

Chinese finger traps.
A bag of paper shreds (you know, the paper stuff people put in packages as "dressing"? Just a bag of that, and nothing else)
You mentioned a pet rock.  Just go out, pick up a rock, paint a face on it, and "sell" it as a solar-powered, off-the-grid, ultra-green pet that never needs feeding, watering, walking,  etc.  (Although for a giggle, I've seen one packaged with a tiny folded-newspaper 'litter box' and care instructions)
I've seen "Fake chest hair"
small containers of pet treats, especially if you know nobody owns a cat/dog  (or fish food)
I've seen plastic gloves that were blown up, and then drawn on to create smiley faces, turkeys, reindeer, etc. 
A small sheet of bubble wrap
fly swatter
Toilet paper cozy (you know, the things you put over rolls of TP to "hide" them.  My grandmother made truly hideous ones in the 70s.)
corn removal pads
Snowman poop (bag of marshmallows)

Why do I love this suggestion?

[BabyMama]

Oh! One year I brought a Nerf dart gun to a white elephant exchange. It was by far the most popular item.

[Kestrels Nemesis]

I keep trying to suggest to my sister that she needs to put together a luau in a box for her next office white elephant......A bottle of pina colada mix (not including the alcohol) coconut bra, grass skirt, lei, a dashboard hula girl, inflatable flamingo or palm tree, etc.

[Dazi]

Play-doh   

I also suggest the great metal slinky

Silly puddy eggs

[turtleIScream]

Pez dispenser for pet treats

[anonever13]

One year my dad bought a nightlight shaped like the leg lamp from "A Christmas Story" for a white elephant.  He told me it was very popular.