Evolving stage 1s (ES1) are usually very forgettable, but every so often, we get some exceptions to that rule.
Expanded
-Eelektric (NV): Arguably the best ES1. The only one to have spawned it's own archetype. Energy acceleration = good. I don't think I need any more elaboration.
-Gabite (DRX): The Dragon call one. It let you search your deck for a Dragon and add it to your hand. A key part of the Garchomp/Altaria deck. Though Garchomp's the star of the deck, this Gabite made it the easiest stage 2 deck to set up.
Standard (XY on)
-Golbat (PF): Golbat is just as important to the bats strategy as Crobat. Even if we didn't have Crobat, Golbat's viable on it's own merits. Instant damage, free retreat, splashable, and can attack for free if dimension valley is in play.
-Lampent (PF): Two words: Night March. It's not even supposed to hit the field. Just discard it with with battle compressor or ultra ball to power up your Joltiks and Phantumps.
-Doublade (PC): For a DCE and a coin flip (Trick Coin should help), you can false swipe to put your opponent at 10HP left. The combo is with Ariados (AO) (or lasers in expanded) who's poison damage will finish them off after a successful false swipe. Just make sure to have some fire Pokemon ready to deal with grass Pokemon immune to poison from Ariados.
Future
-Haunter (BT): Has a coming into play ability that confuses both active Pokemon. Even better, it's attack poisons and retreat locks the opponents active. If you can find a way to get around confusing yourself (switching out with mystery energy), you have a mini lock. Also, as a psychic Pokemon, it won't be shut off by Wobuffett (yours or your opponents)
-Piloswine (BT): More interesting than notable. The footprints attack already does 50 from Piloswine alone. From there, add 10 damage for each swinnub, 20 for each piloswine, and 40 for each Mamoswine. I mention Mamoswine because you can use Piloswines attack with Memory Shrine, but it will do 20 more damage, have 60 more HP, and a defensive ability. You can also use retreat cost modifiers like Team Aqua's Muk to boost the attack. And being fighting type, you have access to strong energy.
Expanded
-Eelektric (NV): Arguably the best ES1. The only one to have spawned it's own archetype. Energy acceleration = good. I don't think I need any more elaboration.
-Gabite (DRX): The Dragon call one. It let you search your deck for a Dragon and add it to your hand. A key part of the Garchomp/Altaria deck. Though Garchomp's the star of the deck, this Gabite made it the easiest stage 2 deck to set up.
Standard (XY on)
-Golbat (PF): Golbat is just as important to the bats strategy as Crobat. Even if we didn't have Crobat, Golbat's viable on it's own merits. Instant damage, free retreat, splashable, and can attack for free if dimension valley is in play.
-Lampent (PF): Two words: Night March. It's not even supposed to hit the field. Just discard it with with battle compressor or ultra ball to power up your Joltiks and Phantumps.
-Doublade (PC): For a DCE and a coin flip (Trick Coin should help), you can false swipe to put your opponent at 10HP left. The combo is with Ariados (AO) (or lasers in expanded) who's poison damage will finish them off after a successful false swipe. Just make sure to have some fire Pokemon ready to deal with grass Pokemon immune to poison from Ariados.
Future
-Haunter (BT): Has a coming into play ability that confuses both active Pokemon. Even better, it's attack poisons and retreat locks the opponents active. If you can find a way to get around confusing yourself (switching out with mystery energy), you have a mini lock. Also, as a psychic Pokemon, it won't be shut off by Wobuffett (yours or your opponents)
Haunter – Psychic – HP70
Stage 1 – Evolves from Gastly
Ability: Gothic Fear
Once during your turn (before your attack), when you play this card from your hand to evolve 1 of your Pokemon, you may use this Ability. Both Active Pokemon are now Confused.
[P][C] Poison Circle: Your opponent’s Active Pokemon is now Poisoned. During your opponent’s next turn, the Defending Pokemon can’t retreat.
Weakness: Darkness (x2)
Resistance: Fighting (-20)
Retreat: 1
Stage 1 – Evolves from Gastly
Ability: Gothic Fear
Once during your turn (before your attack), when you play this card from your hand to evolve 1 of your Pokemon, you may use this Ability. Both Active Pokemon are now Confused.
[P][C] Poison Circle: Your opponent’s Active Pokemon is now Poisoned. During your opponent’s next turn, the Defending Pokemon can’t retreat.
Weakness: Darkness (x2)
Resistance: Fighting (-20)
Retreat: 1
-Piloswine (BT): More interesting than notable. The footprints attack already does 50 from Piloswine alone. From there, add 10 damage for each swinnub, 20 for each piloswine, and 40 for each Mamoswine. I mention Mamoswine because you can use Piloswines attack with Memory Shrine, but it will do 20 more damage, have 60 more HP, and a defensive ability. You can also use retreat cost modifiers like Team Aqua's Muk to boost the attack. And being fighting type, you have access to strong energy.
Piloswine – Fighting – HP100
Stage 1 – Evolves from Swinub
[F][C] Push Down: Your opponent switches his or her Active Pokemon with 1 of his or her Benched Pokemon.
[F][C][C] Footprints of the Herd: 30+ damage. This attack does 30 damage plus 10 more damage for each [C] in the Retreat Cost of your Swinub, Piloswine, and Mamoswine in play.
Weakness: Grass (x2)
Resistance: none
Retreat: 2
Mamoswine – Fighting – HP160
Stage 2 – Evolves from Piloswine
Ability: Thick Fat
Any damage done to this Pokemon by attacks from your opponent’s [R] or [W] Pokemon is reduced by 30 (after applying Weakness and Resistance).
[F][C][C][C] Primeval Roar: 80+ damage. If you have a Stadium card in play, this attack does 40 more damage. If your opponent has a Stadium card in play, this Pokemon heals 40 HP.
Weakness: Grass (x2)
Resistance: none
Retreat: 4
Stage 1 – Evolves from Swinub
[F][C] Push Down: Your opponent switches his or her Active Pokemon with 1 of his or her Benched Pokemon.
[F][C][C] Footprints of the Herd: 30+ damage. This attack does 30 damage plus 10 more damage for each [C] in the Retreat Cost of your Swinub, Piloswine, and Mamoswine in play.
Weakness: Grass (x2)
Resistance: none
Retreat: 2
Mamoswine – Fighting – HP160
Stage 2 – Evolves from Piloswine
Ability: Thick Fat
Any damage done to this Pokemon by attacks from your opponent’s [R] or [W] Pokemon is reduced by 30 (after applying Weakness and Resistance).
[F][C][C][C] Primeval Roar: 80+ damage. If you have a Stadium card in play, this attack does 40 more damage. If your opponent has a Stadium card in play, this Pokemon heals 40 HP.
Weakness: Grass (x2)
Resistance: none
Retreat: 4