Welcome to my first guide - for our glorious Russian robot overlord: Viktor!

While I cannot call myself a LoL expert in any sense, I've been greatly enjoying Viktor, and have found overwhelming success in play.

Though he's far from easy to play well, and certainly vulnerable for lack of instantaneous CC, Viktor can also become a terrifying, facemeling, laser spewing maniac!

Pros:
Excellent range on harass (Death Ray and even Chaos Storm)
Excellent utility (Scouting bushes with Death Ray, Chaos Storm - Area denial with Gravity Field)
Fantastic CC* (When Gravity Field is used correctly, can change the outcome of teamfights with a single cast)
Moderate damage soak (Power Transfer - can make the difference between one or two auto-attacks and a death)
Surprising burst (Very often under-estimated, particularly so for the range of Chaos Storm)

Cons:
Weak range on Power Transfer (The shield is hardly worth the risk of using it in a 1on1 situation, especially vs any gap-closing melee)
*Delayed effect of CC (The 'deployment' of Gravity Field can often let enemies slip away unscathed and can make it nigh-worthless)
Glitchy hit-detection (Death Ray has a tendency to 'miss' targets that it might otherwise damage - usually clustered minions, for example)
Damage falloff (Where some champions can utterly murder their opponents in quick order, Viktor's burst is rarely enough to kill an enemy from full to dead in a single rotation. This means you will either end up chasing or running after unloading your combo - chasing if you popped your Ultimate, more often than not, retreating otherwise. That said - Death ray is EXCELLENT in both cases!)
Very mana hungry (Self explanatory - but Viktor's skills, particularly R, are expensive! Try to get Golem Buff as often as possible)

The runes listed are a very standard page:
Magic Pen Red
Mana Regen Yellow (I use regen/level, but this is to taste)
Cooldown Reduction Blue (One of my favourites, though others can be substituted)
Movespeed Quints (This one can be replaced with HP, or raw AP - in conjunction with AP reds as well)

Masteries are a standard 21/0/9
The arrangement of points in Utility is to taste - I prefer the Flash cooldown reduction over recall improvement as it is, in my experience, a relatively rare occurence where 1 second of recall will make or break things, but having that flash 15 seconds sooner than your enemy can net you a kill, especially first blood.

I like to start with a Blue gem and one of each pot. This is a very standard start, and one I favour for most all casters I play. If you feel less comfortable, take two HP pots instead. If you wind up in a lane where you can expect to eat heavy harass (Xerath is a good example), boots might be a good first.

Either way, aim to complete your Catalyst and level one Boots as soon as possible.
Rod of Ages is an excellent first item, though there are times I delay it to grab the Hex-Core upgrade first.

A word on Hex-Upgrades - I almost exclusively pick the Blue (Gravity Upgrade). The added mana, regen, cooldown and overall sustainability helps Viktor immensely - not to mention the range increase on your snare turns it from a risky skill into a game-changing, team-disruption bubble of certain doom. The uses for this skill cannot be overstated - though it does take practice learning just when and where to drop it, particularly so the delay between casting and the first tick of slow on your enemies - this can make or break your attempt at a chase, if you manage to snag someone with the leading edge of your bubble or miss by an inch.
That said, the Death Ray upgrade works well if you are just completely stomping the opposition - and is excellent for farming - but the overall usage of your improved Gravity bubble tend to outweigh this benefit in my experience. Power transfer is a unique choice, aimed more towards a tankier, evasive build - though the short range of Power Transfer makes it a risky skill to use in any case, and can lead to quick death - speed boost or no - if engaging champions with dashes and snares of their own.

After netting your Boots 2, Rod of Ages, and Hex Core - it is time to decide. If you are utterly stomping, a Deathcap is your next logical choice.
If things are going decently, try pick up Rylai's. Here you are also afforded the opportunity to grab the Giant's Belt first - for a buffer of health- before completing the rest of the item. I've found plenty of times that I buy the belt, the Blasting Wand, and then build a Deathcap before completing my Rylai.

Ideally, Rylia and Deathcap finish off your build - and leave room for one utility item. My two most common choices here are Banshee's Veil, to help you escape and fight another day, or Lichbane - for destroying buildings and laying the hurt on folks of course. Zhonya's Hourglass is also viable - particularly against AD heavy teams - and works well in conjunction with your ultimate.

R > E > Q > W

Open with E (Death Ray) unless you are attempting a jungle gank - in which case Gravity Field is amazing.
Aim to max E by level 9.
Grab one point in Gravity Field at level 2 or 4 (if not taken first).
Power Transfer takes second priority to Deathray, and obviously the ultimate should be leveled ASAP.

Now here I'm going to expect outrage, horror, confusion, mockery: Why are you leveling E first? Q is so much better! It does more damage, it shields you, has a slightly lower cooldown! Why? Quite simply: Range. The range of your Power Transfer is, frankly, awful. It is a dangerous skill to use for poking - despite the (flimsy) shield buff. That said it is far from useless - and can lay on the hurt at later levels - but it leads to more exposure than Viktor likes!

Death Ray, on the other hand, can be fired well beyond the range of most champions, can be fired on the move, can hit multiple enemies, and even grants vision into bushes/jungle! This skill ROCKS, and once you learn how to use it effectively is, in my opinion, one of the best skills in the game. Not to mention it is incredibly badass to run around firing laserbeams and cackling like a maniac (shift+4 at every opportunity)

Gravity Field is a fickle beast - made most touchy by the brief 'deployment' animation that occurs before your slow starts stacking onto targets. Frankly, it is quite easy to avoid the bubble - and even dropping it directly on an enemy will give them enough time to escape if they remain alert. That said - the size and utility of this spell are incredible for area denial, and for utterly screwing grouped enemies in a teamfight. Much like Veigar's infamous Rage Cage, this spell can be a game-changer if employed correctly. As a bonus, the effect for it is easily overlooked during a chaotic fight, often snaring multiple enemies at once, or at least diverting them from attack and escape for some serious time. Learn to love this spell for offense and defense both!

Chaos Storm, as an ultimate, is a curious thing. While it lacks the sheer face-destroying burst of a direct spell, and the team-melting power of other AOE ultimates, Storm has a very unique middle-ground between the two, offering up a decent (often surprising and fatal) chunk of damage (and a tiny silence) when deployed, and enough lingering DOT to finish enemies caught unawares and swiped with a laser along the way. As a handy bonus, the spell will 'lock on' and track enemy champions of deployed overtop of them - INCLUDING champions that have gone into stealth!! This can utterly RUIN characters that rely on 'tactical' short-term stealth to avoid/engage into fights. When dropped on a teamfight, most enemies will scatter like chickens despite the relatively-low follow-up damage that this skill causes. When used in conjunction with Gravity Field, Storm can be used to herd people to their doom! It also makes for fantastic coverage of Gravity Field - as it is unlikely most will notice the trap being set underneath while a looming scary cloud of electric death is in their face.

There you have it!

Shoot laser.
Laugh like maniac.
Forward the glorious evolution!

Any and all comments/advice are appreciated! I hope this guide helps.