Viola is not a supremely popular instrument (admittedly one of the bits that attracts me to it), so there aren't a ton of videos out there I can study. But of those that I've found, two soloists have emerged as muses/inspirations/etc for me - Anna Serova and Olga Goiya.
In honor of my instructor ditching jury duty and calling me up for a slightly longer lesson than usual this afternoon, I thought I'd share a couple of my favorites:
Olga Goiya performing the finale from Alan Shulman's Theme & Variations for Viola & Orchestra:
And Anna Serova performing Vieuxtemp's Capriccio per Viola Sola (she doesn't allow video embedding, so you'll have to click the link).
I love that Goija looks like she's about to fight someone when she plays.
Both videos sound best if your eardrums are wrapped up in monstrous headphones, but a decent set of speakers will work almost as well.