NOTE: Due to the way mutations are applied, you may have to take multiple serums in succession in order to get a higher chance (or a chance at all) at a powerful mutation.
The trick is keeping the serum active in the body, so just before it starts receding, you should take the next one.

Apart from cancer and other dangerous mutations, the more beneficial ones are described in this list:

Regeneration
- bleed rate -50%
- immunity gain speed +150%
- faster healing and regrowing body parts

One punch arm ("Saitama")
- part efficiency 120%
- VERY strong melee attack (25 dps)
- adds 200 carrying capacity
- manipulation +10%
- melee hit chance +10
- melee dodge chance +16
-> Extremely rare, but OP as well

Poisonous fangs
- part efficiency 80%
- strong toxic bite attack

Cat-like ears
- part efficiency 140%

Eagle-eyes
- part efficiency 140%

Scales
- adds 60 carrying capacity
- armor: sharp: 18%, blunt 12%
- manipulation +10%, moving -5%, bleed rate -10%

Metallic skin
- adds 300 carrying capacity
- armor: sharp: 70%, blunt 40%
- manipulation +25%, moving -30%, bleed rate -90%

Strong arm
- part efficiency 120%
- strong melee attack
- adds 40 carrying capacity
- manipulation +10%

Strong leg
- part efficiency 120%
- adds 160 carrying capacity
- moving +50%

Claws
- part efficiency 100%
- strong slashing attack
- manipulation -15%

Fur
- Minimum comfortable temperature -32
- Maximum comfortable temperature -8

Additional sweat glands
- Maximum comfortable temperature +20
- social impact -20%

Enhanced pheromones
- social impact +150%

Enlarged brain
- social impact +150%
- psychic sensivity +120%
- melee dodge chance +6
- mental break treshold +15%
- research speed +200%
- global learning factor +100%

Desensitized nerves
- pain shock treshold +200%
- mental break treshold -15%

Hypersensitive nerves
- pain shock treshold -80%
- mental break treshold +15%

Enhanced immune system
- immunity gain speed +200%

Weakened immune system
- immunity gain speed -60%

Enhanced reflexes
- melee hit chance +5
- melee dodge chance +8

Weakened reflexes
- melee hit chance -4
- melee dodge chance -6

Negative Vanilla mutations:
- Carcinoma
- Blindness
- Deafness
- Loss of a body part
- Dementia