I've long been a fan of Beethoven's Violin Concerto (1, 2, 3). Here it is played by Yehudi Menuhin.
I also like some of the symphonies. Here's Herbert von Karajan conducting the Seventh Symphony, which I think doesn't get enough attention by comparison to the Third (1, 2, 3? 4?) or the Fifth or the Ninth (1, 2, 3a, 3b, 4). Why is it the only even-numbered Beethoven symphony you ever hear is the Sixth? In fact, none of Beethoven's power-of-two symphonies (numbers 1, 2, 4 and 8) get much airplay. Wierd.