Your favourite instructive papers in combinatorics?

[Gordon Royle]

I'm teaching a small combinatorial algorithms / combinatorial 
enumeration unit this semester, trying to cover a range of topics from 
the classical (generating permutations, partitions etc) through 
elementary Polya-counting, bijective proofs and computational 
techniques like orderly algorithms.

One thing I want to do is to give each student a paper on which they 
have to prepare a 25-minute talk, so I am trying to choose good, 
instructive, interesting, but not overly technical papers in the entire 
broad area of combinatorial algorithms/enumeration/computing.

I have my own favourites - Ron Read's paper "Every one a winner" on 
orderly algorithms is one example, but would like to know what other 
gems I should consider....  Expository work such as textbooks or survey 
papers is as welcome as research papers.

As most combinatorial enumerating and computing ends up with sequences, 
I thought that many seqfans would have their own favourites ...

Over to you..

Cheers

Gordon