Pros:
A really hard to kill ad char with his passive and active abilities
Passively is a tank with the item build
Can maul almost any character at any game phase.

Cons:
You will have some difficulty with dedicated tanks (I.e. rammus, skarner, etc.)
Some dedicated AD chars will give you problems 1v1 (Trynd, Yi, Xin)
CC could be a little harsh if the opposing team is CC heavy.

Why an ad build you say? Voli is just supposed to be a tank? But no, Voli can be much much more. Voli can be your table-flippin, om nommer, burrrrrrrrr.

When it comes to runes, I keep it simple. Marks should be your attack speed, Seal is critical damage, Glyphs of Critical chance or speed, your choice. Quintencences should be either attack speed or armor pen, but I like the attack speed choice because it helps your Ionic Spark proc.

I usually rush to warmogs first, with any ad char you need some sort of survivability and 900hp, plus increased hp regen and then an early warmogs gives you more time to bring that passive up. I then get basic boots, rush to atmas, then finish off the boots with mobility, the increase the move 5 helps against those champs who just run away, and it stacks with your flippy flippy. At mid-game should be an ionic spark with a vamp scepter, the lifesteal keeps up your sustain and really helps in case you have that dot on you at low life and you just need a littel health to survive. Late game should be you finishing the inf edge and then bloodthirster. I build the inf edge first because its more ad, and ad is good, and its more crit dmg, which your flip can crit and scale off of. Ever see that ap or ad carry lose a third of their life in one flip? It's beautiful. I sometimes get mercury treads for their tenacity if the CC is a little heavy on the opposing side.

Flip is Voli's bread and butter in this build. Flip adds to your next ad plus a, you guessed it, flip. It's an amazing initiate skill, plus its also your main chase ability. Your W is your next important ability because of the passive, not only is it more attack speed, but the active really helps get that last hit in when they run or munch on that ap that's just chillin. The roar is good, but you only really use it to cause aoe slow, or to make minions scatter and block enemy pathing.

Spells I keep simple, flash/ignite combo. Flash is your either quick escape tool or good chase to get last hit in. Ignite is to really get that last bit of hp away if they run.

Voli is a really great team fighter. He almost does better in team fights than he does 1v1, but its just a slight margin. You want to either flip the squishiest target into the fray, roar, then let your ult start bouncing off of targets. The ionan spark, will cause insta 110 damage spread to up to 4 target about every 1.5 -2 secs which is a great "dot" tool. Try not to get isolated because it is very easy to get overwhelmed and the incoming damage could quite possibly negate your passive. After initiating or flipping a target, chase down any stragglers that try to bolt.

This build is a bit unique because it goes against the usual norm of volibear builds. Most people say "build a tank!" but with the right know how, you tank well enough with this build without all of the dedicated tanking items. Most of the times when I play this build I get top 2 with kills, and if you don't get greedy you can have fewest deaths as well.