My first RMT. Not my first team, but it seems to be one of the more decent ones I've used.
At a glance:
If you have any suggestions for making this team better, or if you just have any questions about it in general, feel free to let me know.
At a glance:






(Pokemon changes will be in Bold. Summary changes will be in Italic.)
B.Y.O.B. (Forretress)@Leftovers
Relaxed Nature
Ability: Sturdy
EVs: 252 HP / 112 Atk / 144 Def
~Stealth Rock
~Toxic Spikes (Change suggested by Iconic)
~Rapid Spin
~Gyro Ball
When I was building this team, I realized that I should have something to set up hazards, as well as remove them. Forretress seemed to be the best one one for the job, due to his Toxic immunity, his resistance to 9 different types, and only one weakness, as well as good defensive synergy with Jellicent, Gengar, and Gliscor. Stealth Rock breaks Focus Sash and Sturdy, as well as nullifying Dragonite's Multiscale, Toxic Spikes help wear down bulky set-up Pokemon, such as Volcarona / Swampert / Virizion, Rapid Spin is pretty self explanatory, and Gyro Ball is for having something to cause some direct damage with, should Forretress get Taunted.
Cheez Ums (Jellicent)@Leftovers
Bold Nature
Ability: Water Absorb
EVs: 252 HP / 224 Def / 32 Sp.Def
~Scald
~Will-O-Wisp
~Taunt
~Recover
Jellicent seemed like a good teammate for Forretress, due to his resistance to Fire, and his immunity to Water. Scald is for being able to hit the opponent, should Jellicent get Taunted, Will-O-Wisp and Taunt help cripple slower support Pokemon, such as Ferrothorn and other Forretress, and Recover is for shrugging off damage.
Brumak (Tyranitar)@Choice Band
Adamant Nature
Ability: Sand Stream
EVs: 180 HP / 252 Atk / 76 Spe
~Stone Edge
~Crunch
~Earthquake
~Pursuit
When I built this team, I had thought about what to use to take care of Reuniclus, who would otherwise cause serious problems for my team. I decided to use a Choice Band Tyranitar, because he could also be used to nullify the rain, which causes serious problems for Pokemon that benefit the most from it, such as Dragonite, or Rotom-W locked into Thunder. Stone Edge and Crunch are for STAB, Earthquake is for hitting grounded Steel types, and Pursuit is for hitting any Psychic or Ghost types trying to get out without a scratch, such as Latios locked into something other than Draco Meteor (which would be likely against this team, because people seem to enjoy predicting my switch into my walls), Chandelure, or the aforementioned Reuniclus.
Starburst (Jirachi)@Leftovers
Impish Nature
Ability: Serene Grace
EVs: 240 HP / 160 Def / 76 Sp.Def / 32 Spe
~Wish
~Body Slam
~Iron Head
~Fire Punch (Change suggested by Alpha Wolf)
I decided to run a defensive Jirachi because aside from Jellicent, none of my team members have reliable recovery, and Jirachi just seemed to fit the bill when it came to this type of support. Wish is obviously the crux of this set, being able to restore 200 HP to any of my team members that need it, Body Slam is for paralyzing my opponent's Pokemon (Not to mention it helps Tyranitar get some KOs), and Fire Punch is for dealing super effective damage against Steel types, such as Skarmory / Ferrothorn / Magnezone, as well as the possibility of a Burn.
(Change suggested by Alpha Wolf)
R.K. Shawn (Gengar)@Leftovers
Timid Nature
Ability: Levitate
EVs: 4 HP / 252 Sp.Atk / 252 Spe
~Substitute
~Disable
~Shadow Ball
~Focus Blast
With effective ways of shutting down certain Pokemon that give my other teammates trouble, Gengar makes an excellent replacement for the Hydreigon that used to be on this team. Substitute and Disable provide an effective way of scouting and neutralizing any opposing Choiced attackers (provided Gengar outspeeds the opposing Choiced attacker), as well Reuniclus that don't run Shadow Ball, and Conkeldurr that run Payback / Stone Edge. Shadow Ball is there for STAB, and Focus Blast provides Gengar with Ghost / Fighting coverage, which isn't resisted by anything.
(Change suggested by Iconic)
Elise (Gliscor)@Toxic Orb
Impish Nature
Ability: Poison Heal
EVs: 252 HP / 184 Def / 72 Spe
~Protect
~Taunt
~Earthquake
~Ice Fang
This used to be a Salamence, but then Iconic made it clear to me that I didn't have anything for Excadrill. (Jellicent has a 20.51% chance of taking 1 Earthquake after Stealth Rock damage, and hitting back with Scald or Will-O-Wisp, but Scald causing the Burn isn't always guaranteed, and Will-O-Wisp doesn't have that good accuracy.) He suggested that I either replaced Salamence with Gliscor, or Jirachi with Bronzong, and this team really needed the Wish support provided by Jirachi (I should probably bring up that even if Excadrill manages to get up to +6 with a Burn {provided Jellicent manages to Burn it beforehand}, it still won't 2HKO with its coverage moves). Protect is for scouting, as well as guaranteeing that the Toxic Orb will activate, Taunt is for preventing any stat boosts or hazards from being set up, such as Spikes / Stealth Rock / Leech Seed from Ferrothorn, Swords Dance from Excadrill, or Wish from Jirachi / Blissey, Earthquake is for STAB, and Ice Fang is so Gliscor has something to pop Air Balloon, should the opposing Pokemon be holding one.

B.Y.O.B. (Forretress)@Leftovers
Relaxed Nature
Ability: Sturdy
EVs: 252 HP / 112 Atk / 144 Def
~Stealth Rock
~Toxic Spikes (Change suggested by Iconic)
~Rapid Spin
~Gyro Ball
When I was building this team, I realized that I should have something to set up hazards, as well as remove them. Forretress seemed to be the best one one for the job, due to his Toxic immunity, his resistance to 9 different types, and only one weakness, as well as good defensive synergy with Jellicent, Gengar, and Gliscor. Stealth Rock breaks Focus Sash and Sturdy, as well as nullifying Dragonite's Multiscale, Toxic Spikes help wear down bulky set-up Pokemon, such as Volcarona / Swampert / Virizion, Rapid Spin is pretty self explanatory, and Gyro Ball is for having something to cause some direct damage with, should Forretress get Taunted.

Cheez Ums (Jellicent)@Leftovers
Bold Nature
Ability: Water Absorb
EVs: 252 HP / 224 Def / 32 Sp.Def
~Scald
~Will-O-Wisp
~Taunt
~Recover
Jellicent seemed like a good teammate for Forretress, due to his resistance to Fire, and his immunity to Water. Scald is for being able to hit the opponent, should Jellicent get Taunted, Will-O-Wisp and Taunt help cripple slower support Pokemon, such as Ferrothorn and other Forretress, and Recover is for shrugging off damage.

Brumak (Tyranitar)@Choice Band
Adamant Nature
Ability: Sand Stream
EVs: 180 HP / 252 Atk / 76 Spe
~Stone Edge
~Crunch
~Earthquake
~Pursuit
When I built this team, I had thought about what to use to take care of Reuniclus, who would otherwise cause serious problems for my team. I decided to use a Choice Band Tyranitar, because he could also be used to nullify the rain, which causes serious problems for Pokemon that benefit the most from it, such as Dragonite, or Rotom-W locked into Thunder. Stone Edge and Crunch are for STAB, Earthquake is for hitting grounded Steel types, and Pursuit is for hitting any Psychic or Ghost types trying to get out without a scratch, such as Latios locked into something other than Draco Meteor (which would be likely against this team, because people seem to enjoy predicting my switch into my walls), Chandelure, or the aforementioned Reuniclus.

Starburst (Jirachi)@Leftovers
Impish Nature
Ability: Serene Grace
EVs: 240 HP / 160 Def / 76 Sp.Def / 32 Spe
~Wish
~Body Slam
~Iron Head
~Fire Punch (Change suggested by Alpha Wolf)
I decided to run a defensive Jirachi because aside from Jellicent, none of my team members have reliable recovery, and Jirachi just seemed to fit the bill when it came to this type of support. Wish is obviously the crux of this set, being able to restore 200 HP to any of my team members that need it, Body Slam is for paralyzing my opponent's Pokemon (Not to mention it helps Tyranitar get some KOs), and Fire Punch is for dealing super effective damage against Steel types, such as Skarmory / Ferrothorn / Magnezone, as well as the possibility of a Burn.

(Change suggested by Alpha Wolf)
R.K. Shawn (Gengar)@Leftovers
Timid Nature
Ability: Levitate
EVs: 4 HP / 252 Sp.Atk / 252 Spe
~Substitute
~Disable
~Shadow Ball
~Focus Blast
With effective ways of shutting down certain Pokemon that give my other teammates trouble, Gengar makes an excellent replacement for the Hydreigon that used to be on this team. Substitute and Disable provide an effective way of scouting and neutralizing any opposing Choiced attackers (provided Gengar outspeeds the opposing Choiced attacker), as well Reuniclus that don't run Shadow Ball, and Conkeldurr that run Payback / Stone Edge. Shadow Ball is there for STAB, and Focus Blast provides Gengar with Ghost / Fighting coverage, which isn't resisted by anything.

(Change suggested by Iconic)
Elise (Gliscor)@Toxic Orb
Impish Nature
Ability: Poison Heal
EVs: 252 HP / 184 Def / 72 Spe
~Protect
~Taunt
~Earthquake
~Ice Fang
This used to be a Salamence, but then Iconic made it clear to me that I didn't have anything for Excadrill. (Jellicent has a 20.51% chance of taking 1 Earthquake after Stealth Rock damage, and hitting back with Scald or Will-O-Wisp, but Scald causing the Burn isn't always guaranteed, and Will-O-Wisp doesn't have that good accuracy.) He suggested that I either replaced Salamence with Gliscor, or Jirachi with Bronzong, and this team really needed the Wish support provided by Jirachi (I should probably bring up that even if Excadrill manages to get up to +6 with a Burn {provided Jellicent manages to Burn it beforehand}, it still won't 2HKO with its coverage moves). Protect is for scouting, as well as guaranteeing that the Toxic Orb will activate, Taunt is for preventing any stat boosts or hazards from being set up, such as Spikes / Stealth Rock / Leech Seed from Ferrothorn, Swords Dance from Excadrill, or Wish from Jirachi / Blissey, Earthquake is for STAB, and Ice Fang is so Gliscor has something to pop Air Balloon, should the opposing Pokemon be holding one.
If you have any suggestions for making this team better, or if you just have any questions about it in general, feel free to let me know.