The way that most pros/high level Varus players play him is for him to Spam Q relying on the team's tanks and supports to CC enemies in place for Varus's safety. You kind of just poke people with max Q damage and go in when you think you can burst them down with all of his other abilities.
Well anything works with Sated Devourer, you could try getting nocturne.
You can set up really sneaky gank with his ultimate, as in hide your team mates from the enemy's vision for them to gank a lane in top lane whilst you gank bot lane. That requires co-ordination though. I've personally had that happen to me a couple of times with the ganker hiding in the bushes, didn't see them because they snuck in whilst Nocturne's ultimate was clouding my vision.
I find that Pantheon is a strong pick against really mobile champions like Yasuo and Kalista for his targetted stun. The stun itself won't keep them in place look enough, typically but it provides a brief time for your team mates to follow up with their stuns and snares to keep Kalista in place for much longer - long enough to delete them.
Pantheon is really good at taking down low health carries.
Pantheon is a great counter to Nasus, Wukong and Rengar, a few champions who use basic attacks to channel their high damaging abilities through. Pantheon's passive lets him block complete 100% damage from their basic attacks, or ability modified basic attacks.