Vi is a straight- up fighter who's shield passive can make her deceptively tanky.
Her W ability shreds armor with each hit (even with abilities) and with 3 successful strikes, reduces the enemy's armor even further, inflicts bonus damage on the third hit, AND grants Vi bonus atk speed for a slight duration.
Vi's Q requires a charge duration that will propel her a distance based on the time charging and plows through minions or stops at the first champion hit.
Vi's E ability sends out a shockwave originating from the unit hit and extends out behind that unit in a cone, inflicting damage on all units inside the area of effect.
Finally, Vi's R ability, though requires a single target, propels Vi to the target, knocking them into the air and finishing with a slam dunk; both the knock up and the follow-up slam inflict damage, but only the slam applies on-hit affects. During the dash to her target, she is immune to slows and snares, but all of which can be applied once the attack ends.

Typically in a match, I like to initiate with Vi's Q ability from behind terrain. This allows me enough time to align my shot and typically catches opponents off-guard. win- win, right? Once the Q hits, I follow- up with an immediate E, basic attacks, E again, and if they're still alive, finish with my ult... that is if they choose to Flash or Ghost away.
A lot of you may find difficulty in believing my build is effective, and I agree; there are a lot of kinks I need to work out. but for now, this is the fruit of my ongoing play with Vi. I would appreciate any tips or suggestions.
As for runes, well, I leave that up to personal preference. Tanky is good, but so is armor reduction and CD reduction...
Thanks for viewing my FIRST GUIDE EVER!
Have a good one and happy hunting!