Beethoven frequently employed exotic sonorities throughout most all of his works, though more frequently later in life. One great example of Beethoven's use of an Augmented Sixth chord is in measure 46 of the Rondo of his Pathetique Sonata (the third movement).
The chord is spelled Cb Eb F A which constitutes the le, do, fi required for any time of augmented sixth chord. Noticing the F present, we may conclude that this Augmented Sixth chord is in fact a French Augmented Sixth chord which adds even more dissonance to this pre-dominant chordal function.
The chord preceding is a IV6 chord (spelled Ab C Eb key: Eb major) which has a duration of a half-note, similar to the augmented chord itself, and the Bb triad (V) following.
Overall, this is a textbook example that properly sets up and executes the harmony in a traditional manner.
In performing this passage, one must account for the numerous leading tones and the strength that they want to resolve. Also, the performer must also notice the particularly lengthy duration of these three sucessive chords and appropriately bring out this deviating harmony (like a secondary dominant function). Amidst this fast paced rondo, there really isn't much time to breathe, so the chord should not be dwelled upon, however it should most definitely have the weight of a brief, yet significant half-cadence.