Choice Items are one of the bigger double-edge swords in this meta. Do you really want to be locked into a certain move, even though the payoff for getting "Choice-Locked" is certainly worth the risk, you can really get into trouble at the same time if used incorrectly. I won't copy the post below, but I will attempt to give a few good Choice Item sets and explain their effectiveness in the current Doubles Metagame here on Smogon (PS!).
The first I am going to post may be a bit cliche, but the set works well. I'm talking about Choice Scarf Landorus-Therian.
Landorus-Therian @ Choice Scarf
Trait: Intimidate
EVs: 252 Atk / 252 Spe / 4 HP
Jolly/Adamant Nature
-Earthquake
-Rock Slide/Stone Edge
-U-Turn
-Filler
ScarfLandog is one of, if not the most, common Landorus-Therian set in the current Doubles Metagame, and rightly so. While it lacks the help of Yache Berry, or the surprise factor of Normal Gem Explosion, or even Focus Sash, it still has a ton of merits, mainly being a fast way to switch and come back to spam Intimidate. It's 91 Base Speed, while not stellar, give it enough speed to outrun many things and hit hard. U-Turn is a great disruption tool against Cresselia, thinking it can spam Icy Wind against it, giving it a second chance to come in and wreak more Intimidate havoc on the other team. This guy actually makes a very good VoltTurn pair with the below mentioned Specs/Scarf Rotom-W, as Rotom can eat the Ice attacks aimed at Lando, while Lando can stomach Grass types at least neutrally. While this set lacks the more immediate power of, say, a Choice Band, it still has a monstrous 145 Base Attack, able to dent so many things not immune to Earthquake, or spamming a very fast Rock Slide to try and Flinch the opponent into submission.
Speaking of Scarfed Rock Slide Spam, the next set may seem a bit out there as far as most Ladder players are concerned, and it hasn't seen a lot of usage lately for some reason. This next mon I'm going to talk about is Choice Scarf Terrakion.
Terrakion @ Choice Scarf
Trait: Justified
EVs:
252 Atk / 252 Spe / 4 HP EVs: 8 HP / 164 Spd / 116 Def / 220 Atk
Adamant Nature
-Rock Slide
-Close Combat
-X Scissor
-Earthquake
(EVs adjusted after Laga's post below)
Choice Scarf Terrakion is one of the fastest Scarfers available in the metagame, only outsped by the Lati's, of which you won't usually see, as Latios likes Dragon Gem more than Scarf, and Latias is way down at around 40ish even in the 1850 stats, and usually is seen running a support set. 130 Base Attack STAB Rock Slide is a fantastic thing, as Rock is a great attack typing in the Doubles metagame. The extra Flinch chance is just icing on the cake, as is the powerful spread move without the headache of playing around with Protect or Flying/Levitate that EQ users have to deal with. Some folks might be surprised to not see Choice Band slapped on here, as 108 Base Speed is still very fast, and CB Rock Slide is pretty threatening, but I prefer the speed offered by Scarf, which lets me outrun and KO Latios, while not getting outsped by mid-speed Scarfers like Cloyster (but I'll get to that later). If you wish, Choice Band is also a great set, but I would slash Quick Attack onto X Scissor or EQ, as you're going to want Priority if you're going to forgo a bit of speed for more raw power.
Now that I've hit a couple physical powerhouses, I'm going to shift focus over to some more Specially oriented Choice mons. The first is Choice Specs Politoed.
Politoed @ Choice Specs
Trait: Drizzle
EVs:
252 HP / 252 SpA / 4 HP 252 HP / 194 SAtk / 58 SDef / 4 Spd
Modest/Timid Nature
-Surf
-Hydro Pump
-Ice Beam
-Hidden Power Electric/Grass
(Edited my EV Spread after Audiosurfer's post below)
This little guy is a certified monster. There's very little that can stomach Choice Specs Hydro Pump in the rain without absorbing it entirely (Jellicient/Gastrodon) or 4x Resisting it (Kingdra). If you don't want to deal with the miss chance, or are just spamming with Gastrodon, Surf is a great option to either Slash, or as its own option entirely in case you want the power option. This guy is a good idea if you really don't ABSOLUTELY want to keep Politoed around forever, or just don't mind losing him. While some may see this set as inferior to standard Defensive Toed, I see it more as a powerful alternative, as it doesn't just sit around Scalding all day then switching out to reset Rain, making it little more threatening to your opponent. This set can also be used as a Water Gem set, but that is a discussion for another week's topic, and I'm not in charge of that.
Finally, I will do one last mon that has been a new addition in the Doubles metagame, as it is banned in VGC. I'm talking about Choiced Kyurem-Black.
Kyurem-Black @ Choice Scarf (or Band)
Trait: Terravolt
EVs: 252 Atk / 252 Spe (or HP) / 4 Def
-Outrage/Dragon Claw
-Fusion Bolt
-Ice Beam
-Earth Power
Kyub is one of those mons that we probably haven't completely explored in Doubles (ok, yes we have, we even have a Power Herb Set) due to it's banned nature in VGC. This gives us a good opportunity to run weird things that some people that are used to Doubles might not think of, and Kyub is one of them! With a monstrous 170 Base Attack (!) and a very decent 120 Special Attack, Mixed Scarf Kyub is just a really great mon to throw around. Despite his weakness to Bullet/Mach Punch, Neutrality to Fire, and Rock Slide weakness, it's so bulky (125/100/90) that it really doesn't always care what's getting thrown at it, because chances are, it'll live it, and then hit back really effing hard. Scarfing it gives you a Base 95 Speed mon, but faster. And it still hits like a truck, even with Dragon Claw. Outrage can be used as well, although locking yourself into it might be bad for you if you miss the mon you want to hit, or it Protects. If it doesn't though, watch out, because the Kyub Truck will plow through it indifferently.
I think that about does it for me though. Just keep in mind that Choice Items ARE effective in Doubles, but you may want to look at whether or not another item, like Life Orb, Expert Belt, or a Gem, will do a better job.