Hah this is great!A camera. It resembles an expensive 35mm SLR camera, except that the camera body is too thin. Closer inspection will discover that there is no mechanism for loading film into the camera, and there is a dial on the back with settings like "3x5," "4x6," "5x7," "8x10," "Slides," "Photo CD," etc. If the camera is used, a Federal Express parcel arrives at the user's current residence at noon the next day. It will contain negatives for any pictures taken, plus the specified prints/slides/etc. If the parcel is traced, the FedEx records indicate that the user sent the parcel to himself, and paid cash.
A bundle of papers and floppy disks containing source code and executables for a huge and complex program with a single input - the length of time it should run for. Unfortunately there is a bug in the program; however long it runs it will always just print "42" before terminating.
A huge (3' x 5' x 8') tin of Spam. The key is to scale.
That rare first draft of the U.S. Constitution with the word "suckers" in it.
A vintage Star Trek lunchbox (original series) with a label that says "Property of Erwin Schrodinger". Inside is a bologna sandwich, either with mustard or without.
A Lego (tm) set and instructions. Put together, it makes a accurate model of a concentration camp.
A bottle marked "diet pills." Anyone taking one will be elated to find it has only 1/16th the calories of a normal pill.