A few from me:
Two young sisters, both learning piano, who are working cooperatively rather than competitively. Both of them follow directions and their practice is very effective. The younger sister asked me to give her more material to work on!
An adult banjo student who has picked up the style incredibly quickly. Like the girls I mentioned earlier, he practices at least an hour a day, and his practice is super-effective. Last night at his lesson we played several duets, with me on guitar and him on banjo. Then he asked me about the theoretical foundations of rhythm guitar, including chord inversions and harmonization! Cue a highly technical discussion at the piano, touching everything from diatonic chords, major vs. minor vs. modal (much of the repertoire in this style is Mixolydian), primary chords in major vs. Mixolydian, common progressions and cadences, stylistic appropriateness of progressions and cadences, and even relative minor chords and when it is stylistically appropriate to susbstitute them... All this with a banjo student who soaked it all up!
An adult piano student who is the most ambitious I have ever encountered, and has the dedication and hard work to match! She practices, on average, three hours a day on average. Distinctions at Grade 1 and Grade 2. Taking Grade 5 theory in two weeks' time, scoring Distinction on practice papers. She actually scored 100% on one of last years' past paper. I fully expect her to score a Distinction on the exam. The first time she came to my studio, she brought a long list of music she wanted to play, ranging in difficulty from the Bach/Petzold Minuet in G all the way up to Chopin's Revolutionary Etude. She has her eyes set on a DipABRSM and perhaps even higher. This morning she told me that she eventually wants to play the Bach/Busoni Chaconne in D minor, which is from the FRSM syllabus! She tore through a big compilation of Grade 2 music, and is now working through the Grade 3 syllabus pieces (which are giving her plenty to chew on, thankfully) before she chooses her three exam pieces. Her scales and arpeggios are coming along great.
Another adult piano student, who was formerly a trombonist. He has a passion for performing publicly, and also for music theory. Sometimes we spend more than half of each lesson studying theory. He was asking me last night about the advanced theory exams, including AMusTCL. He hasn't committed to that track (and I'm not going to push him too hard) but it's great to teach a student who is as passionate about theory as I am!