(Note: This was originally part of a larger general uber stat guide, but I'm a lazy bum, and I've been 'writing' it for a few weeks now, but found myself constantly referencing this, so I decided to post this now)
This is the easiest stat to do, and as such, it's what I'm going to start with. Note that for some of these, you might want to go more than just 1 speed above, unless it's listed as the maximum for a Pokemon you want to beat, as some people put 8-12 EVs in to beat stuff designed to just beat them.
176: Metagross' and Skarmory's minimum speed. If you are using a Metagross with Pursuit, Rock Slide, or Shadow Ball, then you're probably best off raising your speed to 180, to beat...
179: Shedinja's maximum (basically 100% of them) without nature. With the rarity of Tyranitar and spikes, and with most Pokemon like Kyogre and Latias and Latios (Lati@s) unable to hit Shedinja, this thing can be quite the beast when used right. Spikes Deoxys-L is slowly rising in use, however.
193: This is where -speed Groudon sits at with HP Bug. This is generally a Choice Bander with Overheat as the fourth move. This is not anywhere near standard, however, as Groudon doesn't need special attack to OHKO most of the things it would be Overheating, namely Skarmory.
200: This is the absolute minimum for Chlorophyll/Swift Swim Pokemon; it beats max speed Deoxys-F without a speed nature.
203: -Speed natured Rayquaza might sit here. However, the only time a person would likely use such a Rayquaza is with special Rayquaza that has Brick Break for Blissey, as that allows it to nearly 2HKO without any EVs. The standard Rayquaza is a CBer, however, and thus this is not very important.
216: Adamant tankish Groudon and Modest bulky Kyogre hover at 216 (215 for HP Bug Groudon, which is most of them). Deoxys-L also sits here.
225: Adamant Rayquaza has 225 speed as its minimum. Non-standard, but gaining popularity.
231: Speed Chlorophyll Pokemon need to beat out Salaced Groudon and Jolly Ninjask.
256: Lugia without speed. Lugia is a tank, and does not necessarily need speed to beat stuff. Getting in an attack before a recover could be the difference between a KO and running out of PP on Pressure.
267: Speed Dragon Dancing Rayquaza needs to beat out Deoxys-F after 1 DD. The threat of Extremespeed is usually enough to scare them away, however, and the fact that Rayquaza is usually CBed prevents a switch in, so I'd recommend going either lower if you're concerned about post-DD speed, or faster to beat something important. For example...
274: Smeargle. Spore, Belly Drum, Substitute, Baton Pass. This is quite evil when passed to Rayquaza, Deoxys-F, or Medicham, as it will sweep your team if you let them pass. If you outspeed Smeargle, however, you can KO it before it sets up. You still have to watch out for the Endure, Spore, Endeavor, Extremespeed/Dragon Rage Smeargles (Seismic Toss if you're deadly afraid of Blissey and don't want to use Extremespeed, as that is the only Pokemon Dragon Rage will not kill after leftovers). Some subbing Kyogre beat this.
279: Adamant Groudon and Modest Kyogre's maximum. Most of them are at this speed.
288: Standard Adamant Rayquaza is here at maximum, usually one less due to Hidden Power.
306: Jolly Groudon and Timid Kyogre top out at 306. Nearly all Groudon and Kyogre not at 279 are 306. This is the speed around which the uber Metagame is centered, as these two Pokemon are simply so overwhelming if given the chance to sweep.
307: As I said, Groudon and Kyogre are powerhouses. This is where just about everything that can hit does hit. Most Lati@s, Lugia, Gengar, etc. are at this at the minimum. Some go more to try and beat others trying to beat Groudon/Kyogre, which can get kind of insane.
317: Jolly Rayquaza's maximum speed. Most go max speed Adamant, but some like Jolly to always beat Kyogre/Groudon.
319: The max speed for Latias and Latios (Lati@s) without a nature. I rarely encounter Timid Lati@s, as Modest easily beats the most important breakpoint.
339: Modest Sceptile. HP Ice puts it at 338 if they don't EV for max speed. Sceptile, although rare, has the potential to really screw up a lot of ubers, since it has a OHKO (with Overgrow activated) on Kyogre and Groudon, and a guaranteed OHKO on Rayquaza with Petaya HP Ice. Blissey, Lugia, and other special walls are met with swift Leech Seed, or, even worse in some cases, Endeavor, which screws up high health Pokemon even when at half health. That's why I feel this is important enough to mention here.
349: Adamant Swellow. Few teams have sleep takers, and Swellow easily outspeeds the majority of the uber Metagame. In a place where only Metagross and Shedinja resist normal, Swellow reigns supreme. Well, not really, but it's still deadly. It 2HKOs just about everything, making it a good finisher. It can also switch into a few things, unlike Deoxys-F, so it's not completely outclassed (Groudon Earthquake/HP Bug/Overheat, for example).
350: Timid Lati@s, which, as I said, is far from standard. Mewtwo usually tries to beat this.
359: Modest Mewtwo's max speed. Most just go for 351, though.
394: Timid Mewtwo. Very rare.
399: Standard Deoxys-F (maximum). Very deadly.
419: Standard (adamant) Ninjask. Uncommon.
438: Jolly Deoxys-F's max speed. Neutral speed nature is usually fast enough, though. Jolly can be nice to beat stuff like other Deoxys-F and Exeggutor, who try and just beat out this space mutant.
459: Jolly Groudon after a Salac Berry
460: Jolly Ninjask. Rare.
As I add more to the rest of the guide, I'll put in more speeds as time goes on, but these are the main ones.
This is the easiest stat to do, and as such, it's what I'm going to start with. Note that for some of these, you might want to go more than just 1 speed above, unless it's listed as the maximum for a Pokemon you want to beat, as some people put 8-12 EVs in to beat stuff designed to just beat them.
176: Metagross' and Skarmory's minimum speed. If you are using a Metagross with Pursuit, Rock Slide, or Shadow Ball, then you're probably best off raising your speed to 180, to beat...
179: Shedinja's maximum (basically 100% of them) without nature. With the rarity of Tyranitar and spikes, and with most Pokemon like Kyogre and Latias and Latios (Lati@s) unable to hit Shedinja, this thing can be quite the beast when used right. Spikes Deoxys-L is slowly rising in use, however.
193: This is where -speed Groudon sits at with HP Bug. This is generally a Choice Bander with Overheat as the fourth move. This is not anywhere near standard, however, as Groudon doesn't need special attack to OHKO most of the things it would be Overheating, namely Skarmory.
200: This is the absolute minimum for Chlorophyll/Swift Swim Pokemon; it beats max speed Deoxys-F without a speed nature.
203: -Speed natured Rayquaza might sit here. However, the only time a person would likely use such a Rayquaza is with special Rayquaza that has Brick Break for Blissey, as that allows it to nearly 2HKO without any EVs. The standard Rayquaza is a CBer, however, and thus this is not very important.
216: Adamant tankish Groudon and Modest bulky Kyogre hover at 216 (215 for HP Bug Groudon, which is most of them). Deoxys-L also sits here.
225: Adamant Rayquaza has 225 speed as its minimum. Non-standard, but gaining popularity.
231: Speed Chlorophyll Pokemon need to beat out Salaced Groudon and Jolly Ninjask.
256: Lugia without speed. Lugia is a tank, and does not necessarily need speed to beat stuff. Getting in an attack before a recover could be the difference between a KO and running out of PP on Pressure.
267: Speed Dragon Dancing Rayquaza needs to beat out Deoxys-F after 1 DD. The threat of Extremespeed is usually enough to scare them away, however, and the fact that Rayquaza is usually CBed prevents a switch in, so I'd recommend going either lower if you're concerned about post-DD speed, or faster to beat something important. For example...
274: Smeargle. Spore, Belly Drum, Substitute, Baton Pass. This is quite evil when passed to Rayquaza, Deoxys-F, or Medicham, as it will sweep your team if you let them pass. If you outspeed Smeargle, however, you can KO it before it sets up. You still have to watch out for the Endure, Spore, Endeavor, Extremespeed/Dragon Rage Smeargles (Seismic Toss if you're deadly afraid of Blissey and don't want to use Extremespeed, as that is the only Pokemon Dragon Rage will not kill after leftovers). Some subbing Kyogre beat this.
279: Adamant Groudon and Modest Kyogre's maximum. Most of them are at this speed.
288: Standard Adamant Rayquaza is here at maximum, usually one less due to Hidden Power.
306: Jolly Groudon and Timid Kyogre top out at 306. Nearly all Groudon and Kyogre not at 279 are 306. This is the speed around which the uber Metagame is centered, as these two Pokemon are simply so overwhelming if given the chance to sweep.
307: As I said, Groudon and Kyogre are powerhouses. This is where just about everything that can hit does hit. Most Lati@s, Lugia, Gengar, etc. are at this at the minimum. Some go more to try and beat others trying to beat Groudon/Kyogre, which can get kind of insane.
317: Jolly Rayquaza's maximum speed. Most go max speed Adamant, but some like Jolly to always beat Kyogre/Groudon.
319: The max speed for Latias and Latios (Lati@s) without a nature. I rarely encounter Timid Lati@s, as Modest easily beats the most important breakpoint.
339: Modest Sceptile. HP Ice puts it at 338 if they don't EV for max speed. Sceptile, although rare, has the potential to really screw up a lot of ubers, since it has a OHKO (with Overgrow activated) on Kyogre and Groudon, and a guaranteed OHKO on Rayquaza with Petaya HP Ice. Blissey, Lugia, and other special walls are met with swift Leech Seed, or, even worse in some cases, Endeavor, which screws up high health Pokemon even when at half health. That's why I feel this is important enough to mention here.
349: Adamant Swellow. Few teams have sleep takers, and Swellow easily outspeeds the majority of the uber Metagame. In a place where only Metagross and Shedinja resist normal, Swellow reigns supreme. Well, not really, but it's still deadly. It 2HKOs just about everything, making it a good finisher. It can also switch into a few things, unlike Deoxys-F, so it's not completely outclassed (Groudon Earthquake/HP Bug/Overheat, for example).
350: Timid Lati@s, which, as I said, is far from standard. Mewtwo usually tries to beat this.
359: Modest Mewtwo's max speed. Most just go for 351, though.
394: Timid Mewtwo. Very rare.
399: Standard Deoxys-F (maximum). Very deadly.
419: Standard (adamant) Ninjask. Uncommon.
438: Jolly Deoxys-F's max speed. Neutral speed nature is usually fast enough, though. Jolly can be nice to beat stuff like other Deoxys-F and Exeggutor, who try and just beat out this space mutant.
459: Jolly Groudon after a Salac Berry
460: Jolly Ninjask. Rare.
As I add more to the rest of the guide, I'll put in more speeds as time goes on, but these are the main ones.
