approved by pocket, harsha, birkal and haunter
SPINBLOCKERS
Ignore the Darkrai on the picture
Spinblockers are arguably the best way to avoid your opponent getting rid of your hazards. The only pokémon that can do this are, of course, Ghost-types, as they are immune to Normal-type attacks, including Rapid Spin. It's normally associated with stall teams, as they need to keep hazards up, as they lack offensive presence and must make the opponent take the most passive damage possible. However, spinblocking is also good for offensive teams that want the opponent taking more hazard damage and giving their sweepers an easier time.
That said, there are some problems with spinblocking. For example: There is a lack of Ghost-types that can fit on almost all teams; all of them have a flaw that prevent this. For example, Gengar and Sableye are frail, Jellicent lacks offensive presence, and Chandelure is (ironically) weak to Stealth Rock and vulnerable to all hazards. If you detect a potential pursuiter on your opponent's team, you will need prediction if you don't want to lose your spinblocker. Also, there are some other ways to remove hazards or prevent them from being spinned, that don't require spinblockers, such as Magic Bounce, or using Rocky Helmet on something like Ferrothorn or Deoxys-D. They somewhat reduce the need to use a Ghost-type.
This doesn't mean that spinblocking is not an efficient strategy; preventing the spin of hazards can cost a game. For example, if your opponent's weather inducer is at hazard KO range (generally 12% - Stealth Rock damage when neutral), you have effectively won the weather war as long as you prevent the hazard from being spinned.
Some examples of spinblockers:
Gengar
Gengar is a good spinblocker for offensive teams because it can pose an offensive threat by itself. It is quite versatile; can pull off a variety of sets, most of them wich involve Substitute. However, its frailty means that Gengar will die to most neutral attacks. Also, it is quite vulnerable to Pursuit if not behind a Substitute, but Focus Blast can defeat a common Pursuiter, Tyranitar.
Jellicent
Jellicent tends to be the most durable spinblocker as it packs reliable recovery, but unlike Sableye, it actually has good defenses. It has an ability that prevents your opponent from spamming Water-type attacks with impunity, and Jellicent can also stall out many defensive threats with a combination of Taunt, Will-O-Wisp (or Toxic) and Recover.
Sableye
Sableye at first glance seems to be a pathetic Pokémon. Even though its tipying gives him no weakness, due to its frailty, Sableye is 2HKOed or OHKOed by almost all attacks. However, thanks to Prankster, Sableye can be an annonying Pokémon to face. Depending of the conditions, it can stall out many opponents, and can actually be difficult to KO because of priority Recover. Thanks to Will-O-Wisp, it is almost impossible to defeat him with a physical attacker unless it packs power to OHKO Sableye even when burned. Unfortunately, Sableye is still frail even with defensive investiment, and usually dies to most special attacks due to them not being affected by burns.
Golurk
Golurk has 2 niches. First, it is the only pokémon in the game that can setup Stealth Rock AND spinblock at same time! The second is that Golurk is one of the best counters to Terrakion, a top-threat that ironically has counters only on lower tiers. But hanks to its Ground typing, Golurk loses to Starmie and Tentacruel, two common spinners, as they are Water-types.
Chandelure
Chandelure is a rather interesting spinblocker. Like almost all others, it also has a unique typing, on its case, Ghost/Fire. Its ability means that Chandelure has 3 immunities to switch-in, besides its resistances. However, its Fire typing means that it can also potentially lose to two spinblockers, Starmie and Tentacruel, 1x1. Chandelure is (ironically) weak to Stealth Rock, and vulnerable to Spikes. For these reasons, Chandelure isn't generally considered a good spinblocker. But it is still a great Pokémon, and one for wich exists the most speculation due to its hidden ability, Shadow Tag, wich will potentially make Chandelure a Uber pokémon.
Rotom
Rotom retains the characteristic that was inherent to its -A forms; it's a Ghost-type. It is the only Ghost-type that can keep momentum, thanks to Volt Switch, and it has a great typing. However, Rotom is weak, frail and is not especially fast even with Choice Scarf, as it fails to outspeed some important threats. Despite not being as vulnerable to Tyranitar as other spinblockers, you need to be careful, as Volt Switch cannot avoid Pursuit if Rotom doesn't predict Tyranitar coming in. The same is valid to all other Pursuiters.
Froslass
Froslass has an interesting niche. Like Golurk, Frosslass can setup hazards while spinblocking, but the hazard that Froslass can setup is Spikes. By forcing the opponent to attack, Froslass can then use Destiny Bond and kill their spinner, leaving all the opponent's team vulnerable to Spikes for the rest of match. However, like Chandelure, Frosslass is ironically weak to hazards, and she is very frail and unfortunately has a horrible Ice typing. Any Steel-type will wall and/or defeat Froslass. Scizor is the best example as it can Bullet Punch Froslass before she can use Destiny Bond. Tyranitar can also checkmate Froslass with Crunch and Pursuit, but if it isn't using Choice Scarf, Frosslass may use Destiny Bond and get a free dead Tyranitar.
Cofagrigus
Cofagrigus, unlike most other known Ghost-types lacks a secondary typing. This leaves him with few resistances/immunities to abuse, but at least Cofagrigus doesn't gain common weakness. It has a shallow support movepool, but at least it gets the options that it needs; although its HP is lacking, it has an extremely good physical defense, and a respectable special defense. With max investiment in physical defense and Will-O-Wisp, Cofagrigus has a better physical bulk than even Skarmory. It can, however, also run a Calm Mind set, however that set is generally overshadowed by Keldeo, Jirachi and other Pokémon that may run better CM sets; what Cofagrigus has over them is a good physical bulk.