League: Diamond
Rank: 2nd in division, 613 ELO (yes, relatively new division).

Against Terran my opening is: either a five roach rush or 14 gas, 14 pool. Continue as a one-base muta threat, abort to baneling+expand if bio is scouted.

I use this opening because: without some sort of active pressure or menace, I feel that T can dictate the game too easily. Being able to force moves in a game is the first step in creating a winning strategy, so I want to avoid being cornered - and both builds incorporate a delayed but still relatively early expansion. The current metagame means that most T aren't ready to handle the roach rush, so that's my preferred method at the moment.

Against Protoss my opening is: depending on the map, either 8-pool early pressure or 14 pool, 15 hatch.

I use this opening because: I find that spine+zerglings into hydra is a pretty solid early/mid game defense plan. The choice of hydras greatly discourages stargate tech and the overal composition heavily tempts P to go robotics for colossi, which is a good way to get corruptors and therefore a head start on a very hard-to-deal-with brood lord+hydra strat. However, maps where the defender's advantage is smaller (such as, say, Steppes of War) I find that early pressure (or even just the threat of early zerglings) tends to wreck the plans of many P players of my level and ends up netting me an economical advantage. 

Against Zerg my opening is: 10 gas, 10 pool into banelings. Cut gas after 150 units.

I use this opening because: it gets 4 banelings and 2-6 zerglings (I need to find out the best execution) into the opponent's base before they can set up the much slower 14 gas 14 pool speed first build that most people seem to favor. It still boils down to baneling control like early ZvZ often does, but it ensures that the first strike is mine.

League:Diamond
Rank: 550 ELO(31 in my division)

Against Terran my opening is:
14gas,14 pool on small map
15gas,15pool on bigger maps
I try to take my expansions around 20 supply
Teching to Mutas to pressure the terran

I use this opening because:
U can get a good amount of drones really quick and a fast speed upgrade for ur zerglings to defend against early aggression. Its very flexible so i can react to what hes doing. After i did some harassment with my mutas i react to what hes doing.

Against Protoss my opening is:
14gas,13pool hatchery around 20 supply if he does no 2gate

I use this opening because:
I get the pool a little bit earlier in zvp than in zvt because early zealot pressure is very common and dangerous, and i want lings/my queen/a spinecrawler to defend against it asap without getting behind in economy. Depending on the map his unit composition i get hydras or mutas asap.

Against Zerg my opening is:
13gas,13pool,speed asap, bling nest with next 50 gas

I use this opening because:
I wanna do some pressure with blings, maybe win the game with them, get an expansion up and transition into muta/bling.

League: Diamond
Rank: ~600 Points

Against ALL RACES my opening is:
14 Pool
15 Ovie
17 Queen (Build another immediately after this one finishes)
20 Gas
20 Roach Warren
24 2nd Hatch in Main (When Hatch is ~50%, Lair)

Expand when Lair is complete.

Constant Queen/Drone Production until I have about 8-10. Build enough Roaches to defend any early scouted aggression. Beyond this, spread creep, and build whatever does best against your opponents unit composition.

I use this opening because:

I feel the usefulness of Queens throughout the game (especially early game) is extremely underestimated, and I choose to take advantage of the excellent unit Blizzard gave us. Queens are excellent anti-air, and are great support for your ground army when defending. Transfuse and Creep Tumors are grossly underused, in my opinion, and Queens can prove to be excellent defense against Reapers, Hellions, and other harrass units.

Although your expansion is later than normal, you still have excellent production capabilities due to your extra Hatch in Main, and you can produce as many drones as you could if you were to Fast Expand, but you are significantly less vulnerable to early aggression.

Having so many Queens allows you to literally have half of the map covered in creep within 10 minutes, and obviously spreading creep is extremely valuable as it provides vision of your opponents movement and excellent mobility.

Also, 8 Queens with full energy essentially provides a 3200 HP buffer to your defending army, with their transfuse ability (assuming good micro).

I've only recently adopted this strategy, but in the last 50 ladder games I've played, using this build, I've only lost 13, and I attribute those losses to my own faults (including some things seen below in "key things").

Key things for executing this build:

Be extremely diligent in your scouting. At all times, you should know where your enemy is, what units he has, etc. Queens are great GtG support, but if they're the only thing you have, good luck winning.

Once you have a good defense and your natural expansion is fortified, spread more creep and expand like crazy.

Be on top of Spawn Larva!!!! There is no point to having so many Queens if you're not using their production ability!!!!

Replays:

ZvP 1
ZvP 2

ZvT 1
ZvT 2

ZvZ 1
ZvZ 2


-----------------------------------------------------------------------------

I would also like to say that although I may not be among the pros, I believe this overall strategy has great potential, and I would simply like my idea looked at by top players. I would hope people give this idea a chance (because it has been working for me, excellently) and not just blow it off because I'm only Mid-Diamond.