My nomination would be an obscure, vinyl only LP, from the UK, from 1979.

Charlie Fawn's self titled album.

This LP is a great combination of charm and power pop.  Plus, no slow ballads.
It may not be "classic" power pop, in the way a lot of people think of power
pop, but it's my ideal.

My nomination for best song is the 1st song from that album, called "Hothead
Handshake Tremble."  Both the lyrics and instrumentation are so uplifting,
that it's always the song I go for if I'm trying to feel undepressed (it's the
first power pop song I played after 9/11, when I wanted a change in my mood).
This song, and the 2nd song "Blue Skies", are not too hard to find as 45s. 
The LP tends to be pretty pricey, however.
                                                              
The reason I'm only posting my nomination now, is that I spent the last week
cleaning up the defects in the CDR I had made of it, so now it sounds almost
perfect.  Here's some MP3 samples from the LP (each is the first 2 minutes of
the songs).

http://web.mit.edu/london/www/fawn