Just because a Pokemon hasn't evolved yet doesn't mean it's entirely useless. Many unevolved Pokemon have fantastic stats that many people totally miss, looking instead to their evolutions who typically have better numbers. However, before you're far enough into the game, you may not have access to the evolutionary stages past the base stage.
So, here's a list of Pokemon that haven't evolved yet (but can!) that have very respectable special attack stats. These are great options to look for before you're able to achieve those final evolutions since they have the highest possible special attack for all unevolved forms.
10 Cacnea
Its evolution, Cacturne, may be a terrifying plant demon that stalks its prey under the cloak of darkness, but Cacnea itself puts up decent numbers toward its base stat total even before it evolves. This Grass-type from Generation III may not have the most impressive base stat total of all time — 335 — but it does have very nice special and physical attack stats.
Both measure 85 points, though the physical attack is outclassed by many others. When it comes to special Grass-moves like Energy Ball or Grass Knot, though, Cacnea is a great choice.
9 Smoochum
Baby Pokemon typically don't impress with their stats — they're usually very low and unusable until they evolve. Smoochum is no different, with a base stat total of a meager 305, including a terrible physical defense stat of just 15 points.
However, Smoochum has a surprisingly high base special attack: 85 points, just like Cacnea. Sure, this pales in comparison to its evolution, Jynx, who has a special attack stat of 115. But, for a Baby Pokemon, that's a very decent base stat, showing that Smoochum could hold its own if it needs to.
8 Porygon
Before receiving two further evolutions in future generations, Porygon was a standalone single-stage Pokemon in Generation I, and it had stats that would let it operate well on its own. This is good, too, since it was very hard to get your hands on a Porygon in the first few games in the series.
Porygon — and its evolutions — are experts in special attack. Even before evolving, Porygon has a special attack stat of 85. After evolving, it gets even better. Porygon2 has a special attack stat of 105, and Porygon-Z holds the record alongside Mega Pidgeot and Drampa for the highest special attack of all Normal-types: 135.
7 Omanyte
Fossil Pokemon are typically very decent in their base stage, with many of them excelling in some stat or other before evolving. One of these respectable stats is the special attack of Omanyte, the base stage of the Omastar line from Generation I.
Omanyte has a base special attack stat of 90, which is very nice, especially alongside its physical defense stat of 100. When it evolves into Omastar, that special attack jumps up to 115, which is surprisingly great.
6 Type: Null
Created by the Aether Foundation to take down Ultra Beasts, it's no surprise that Type: Null, the Legendary from Generation VII, has respectable stats even before evolving into Silvally. Other than its base speed, all of its stats are 95, which is pretty good for an unevolved Pokemon.
This, of course, includes special attack, making attacks like Tri Attack and Hyper Beam very powerful on this Pokemon. Type: Null actually has the highest base stat total — 534 — of all Pokemon that can still evolve.
5 Magnemite
Looking at Magnemite, one might assume it excels most in defense. It is a ball of steel with two magnets attached, after all. However, its highest stat is actually special attack, sitting at a nice 95 points. This works well with the many special Electric- and Steel-type moves it learns, like Flash Cannon, Gyro Ball, Discharge, Zap Cannon, and Thunder.
After evolving, its special attack grows a lot. Magneton has a base special attack stat of 120, while Magnezone's is a very high 130.
4 Gastly
Poison- and Ghost-types, on average, have special attack as one of their highest stats. So, it's no surprise that a Pokemon like Gastly, which combines these two types, would excel in that stat as well. Gastly actually has ridiculously high special attack compared to its other stats.
Gastly's other stats are either 30 (HP and defense) or 35 (attack and special defense), while its special attack and speed are extremely high in comparison. For speed, Gastly sits at a nice 80, while in special attack, it puts up 100 points to its total of 310, making special attack about a third of its entire base stat total.
3 Tangela
As another Pokemon that once stood alone as a single-stage, Tangela also has decent enough stats to battle without evolving. While its most respectable stat is the 115 points in physical defense that it has, it also possesses a decent bit of special attack.
Tangela's special attack stat is a nice even 100, meaning it can fire off some great Giga Drains or Solar Beams.
2 Abra
The members of the Alakazam family have always been known for their extremely high special attack. Mega Alakazam actually has the highest base special attack of all non-Legendary Pokemon. So, it's no surprise that the base stage, Abra, also has pretty decent special attack. It ties with Solosis for the top spot amongst all unevolved Pokemon for its special attack.
Despite the fact that it only learns Teleport by leveling up, Abra boasts a special attack stat of 105. Of course, it can learn TMs to put this to use, but in the wild, it's kind of pointless and funny.
1 Solosis
As stated, Solosis ties for Abra at the top spot. It has a base special attack stat of 105, just like Abra does. However, Solosis does have a bit more use for it in terms of naturally-learned moves. Solosis isn't locked to only learning Teleport by level-up.
It can use its special attack stat for moves like Psychic, Psybeam, and Confusion. After evolution, though, the Abra family pulls ahead. Alakazam's base special attack is 135 while Reuniclus' is ten points lower at 125.