So I was questioning whether Lotad was actually a viable Pokemon, or just another "Magikarp, Caterpie, etc." Pokemon, so I asked Heysup, who said Lotad was viable, so here we go!
http://www.serebii.net/pokedex-bw/270.shtml
[OVERVIEW]
- Inferior to most Rain Dance sweepers such as Mantyke and Kabuto because it’s weak
- Frail and mediocre stats all across the board
- Has good STAB options, and good coverage
- Even though it has some small advantages, usually better off using another Rain sweeper
- Rain is not as good as other weathers, because it cannot be set up permanently, but easily removed
[SET]
name: Rain Sweeper
move 1: Rain Dance
move 2: Surf
move 3: Giga Drain
move 4: Ice Beam
item: Life Orb
ability: Swift Swim
nature: Timid / Modest
evs: 36 Def / 196 SpA / 36 SpD / 196 Spe
ivs: 0 HP
[SET COMMENTS]
- Not as powerful as most other Rain sweepers, and though outclassed, it is still viable
- Rain Dance doubles it's Speed, and increases the power of Surf
- Surf for STAB, quite powerful in Rain, most powerful attack
- Energy Ball provides secondary STAB, hits opposing Water-types such as Frillish, who would otherwise wall this set
- Giga Drain can be used, losing a bit of power, but replenishing its own health
- Ice Beam provides more coverage, hits Grass- and Dragon-types who resist both it’s STAB attacks
[ADDITIONAL COMMENTS]
- Timid hits 26 Speed with Swift Swim, Modest hits 24
- Timid outspeeds more Pokemon, Modest can be used for power
- Life Orb is a must to achieve certain KOes
- IVs allow Lotad to only have 19 HP, only losing one HP from Life Orb
- EVs maximize SpA and Spe, increase it’s defense by 1 point
- Entry hazards are very important
- Ferroseed can provide Spikes, Rain means it is only 2x weak to Fire-
- Bronzor is also a good teammate, has the bulk to set up Stealth Rock and Rain Dance, so Lotad does not have to set it up by himself
- Powerful Fighting-type Pokemon such as Dragon Dance Scraggy can take on Special walls such as Munchlax
- Chinchou can deal with Mantyke, a Pokemon Lotad has trouble with
[Other Options]
- Not many other options
- Scald though frail, better off attacking with more powerful attacks
- Swords Dance with Waterfall, Seed Bomb, Zen Headbutt, though will rarely find time to boost, walled by Ferroseed
- Toxic but very frail, usually not worth it
- HP Electric over Ice Beam to hit Mantyke harder, but loses out on hitting Snover for decent damage
- Can set up Rain Dance itself, but coverage is usually more important
- Can run a Rain supporting set with a bulky spread and Evolution Stone or Damp Rock
- Teeter Dance to confuse opponents, but not reliable and Lotad is better off attacking
[Checks and Counters]
- Scarf Snover, takes away Rain, defeats Lotad with Blizzard
- Ferroseed is not weak to any attack, doesn’t mind rain boosted Surfs, can set up Spikes and defeat Lotad with Bullet Seed
- Tentacool also isn’t weak to any of Lotad’s attacks, can take it out with a Slime Wave
- Tentacool can also fire off powerful STAB Hydro Pump in the rain against Lotad's teammates
- Munchlax can take a Rain boosted Surf and KO with Return
- Outside of rain, any relatively fast sweeper can defeat it
- It only hits 13 Speed max, so Pokemon such as Gastly and Gligar can outspeed and take it out
[Dream World]
- It has Own Tempo, but more or less useless
- Most Pokemon would rather attack it than confuse it
- Machop's Dynamicpunch is no longer that common

http://www.serebii.net/pokedex-bw/270.shtml
[OVERVIEW]
- Inferior to most Rain Dance sweepers such as Mantyke and Kabuto because it’s weak
- Frail and mediocre stats all across the board
- Has good STAB options, and good coverage
- Even though it has some small advantages, usually better off using another Rain sweeper
- Rain is not as good as other weathers, because it cannot be set up permanently, but easily removed
[SET]
name: Rain Sweeper
move 1: Rain Dance
move 2: Surf
move 3: Giga Drain
move 4: Ice Beam
item: Life Orb
ability: Swift Swim
nature: Timid / Modest
evs: 36 Def / 196 SpA / 36 SpD / 196 Spe
ivs: 0 HP
[SET COMMENTS]
- Not as powerful as most other Rain sweepers, and though outclassed, it is still viable
- Rain Dance doubles it's Speed, and increases the power of Surf
- Surf for STAB, quite powerful in Rain, most powerful attack
- Energy Ball provides secondary STAB, hits opposing Water-types such as Frillish, who would otherwise wall this set
- Giga Drain can be used, losing a bit of power, but replenishing its own health
- Ice Beam provides more coverage, hits Grass- and Dragon-types who resist both it’s STAB attacks
[ADDITIONAL COMMENTS]
- Timid hits 26 Speed with Swift Swim, Modest hits 24
- Timid outspeeds more Pokemon, Modest can be used for power
- Life Orb is a must to achieve certain KOes
- IVs allow Lotad to only have 19 HP, only losing one HP from Life Orb
- EVs maximize SpA and Spe, increase it’s defense by 1 point
- Entry hazards are very important
- Ferroseed can provide Spikes, Rain means it is only 2x weak to Fire-
- Bronzor is also a good teammate, has the bulk to set up Stealth Rock and Rain Dance, so Lotad does not have to set it up by himself
- Powerful Fighting-type Pokemon such as Dragon Dance Scraggy can take on Special walls such as Munchlax
- Chinchou can deal with Mantyke, a Pokemon Lotad has trouble with
[Other Options]
- Not many other options
- Scald though frail, better off attacking with more powerful attacks
- Swords Dance with Waterfall, Seed Bomb, Zen Headbutt, though will rarely find time to boost, walled by Ferroseed
- Toxic but very frail, usually not worth it
- HP Electric over Ice Beam to hit Mantyke harder, but loses out on hitting Snover for decent damage
- Can set up Rain Dance itself, but coverage is usually more important
- Can run a Rain supporting set with a bulky spread and Evolution Stone or Damp Rock
- Teeter Dance to confuse opponents, but not reliable and Lotad is better off attacking
[Checks and Counters]
- Scarf Snover, takes away Rain, defeats Lotad with Blizzard
- Ferroseed is not weak to any attack, doesn’t mind rain boosted Surfs, can set up Spikes and defeat Lotad with Bullet Seed
- Tentacool also isn’t weak to any of Lotad’s attacks, can take it out with a Slime Wave
- Tentacool can also fire off powerful STAB Hydro Pump in the rain against Lotad's teammates
- Munchlax can take a Rain boosted Surf and KO with Return
- Outside of rain, any relatively fast sweeper can defeat it
- It only hits 13 Speed max, so Pokemon such as Gastly and Gligar can outspeed and take it out
[Dream World]
- It has Own Tempo, but more or less useless
- Most Pokemon would rather attack it than confuse it
- Machop's Dynamicpunch is no longer that common