Powers: (Inspired by) Tentacool

Two tentacles.

The one dumb thing you run into way too much when you finally get the power to swim.

Clear Body

This makes one invulnerable to stat lowering effects. If this is afflictions that lower Attributes or Secondary characteristics, this might be:

Immunity To Attribute/Secondary Characteristic Effects (Common; Reflexive, +40%)[21]

Mental Immunity To Attribute/Secondary Characteristic Effects (Common; Reflexive, +40%)[21] 

This is Common, as it feels a little less powerful than metabolic hazards. If you feel this is actually very common, double the cost. This is reflexive, so if targeted, the bearer may selectively allow the effect to work or not (For example, to allow a buff to work.)

Liquid Ooze

This hurts anyone that uses draining attacks against the target, those that absorb HP. As that seems rarer than fire, I might stat it as:

Damage Resistance 1(Leeching Abilities Only, -60%; Reflective, +100%)[7/level]

Feel free to take as much as necessary, probably 10 is a useful ceiling.

Rain Dish

Recover hit points when it rains. This might be:

Regeneration (Fast; Environmental, Only When It Rains, -30%)[35]

Barrier

This builds up a Force Field around the user, and is cumulative. This is Forcefield DR in GURPS. Look at Reflect, but take it at least at level 2.

Brine

This does more damage to a weaker Foe. This can be represented as a gradient of two abilities:

Corrosive Attack 6d+2 (Accessibility, Only against target with HP Below 50%, -20%; Increased 1/2d, +15%, Sorcery, -15%)[53]

Corrosive Attack 3d+1 (Accessibility, Only against target with HP Above 50%, -20%; Increased 1/2d, +15%, Sorcery, -15%)[27]

So 53 + (1/5 * 27) = 59 points. 17 if taken as an alternate ability.

Brine

Keywords: Leveled, Missile, Obvious

Full Cost: 59 points.

Casting Roll: none, use innate attack.

Range: 100 yards

Duration: Instantaneous

The "caster" soaks the target in burning salty brine. This does 3d+1 corrosion damage, unless the target's HP is below 50%, in which case this is doubled to 6d+2.
Statistics: See above.
Notes: As an alternate ability this move actually costs 17 character points, not 12.

Sludge Wave

This does a huge amount of poison damage to all nearby targets, and then has a chance of doing ongoing poison damage. This is a strong toxic attack with an easily resisted cyclic follow-up.

Sludge Wave

Keywords: Area (Leveled), Obvious, Resisted (HT)

Full Cost: 37.025 for level 1. 11.75 points/level thereafter.

Casting Roll: none, use innate attack.

Range: 2 yard radius.

Duration: 10 seconds of cyclical damage.

The "caster" causes a huge wave of sludge to wash over those around her, immediately dealing 5d-1 toxic damage to those who can't escape. Those that are struck, need to roll HT every turn or are dealt an additional 1 HP of toxic damage. Once resisted, the cyclic damage abates. Level 1 has a radius of 2 yards around the caster, and additional levels double the radius.
Statistics: Toxic Attack 5d-1 (Area Attack, 2 yards, +50%; Emanation, -20%; Sorcery, -15%)[28] + Toxic Attack 1HP(Cyclic, 10 cycles, 1 second, +900%; Follow-Up, Emanation, -20%; Magical, -10%; Resistable, HT, -30%)[10]
Notes: Technically, adding resistable does nothing to reduce the cost; you could have a superior ability for the same price if you removed the resistible limitation.

Other Thoughts and Conclusion

Poison got a really short stick in generation one, I think, but it has gotten a teeny bit better over time. Originally, I don't think there were any really good poison moves beyond Toxic, but now even Tentacool, the filler that is there to annoy you, has a few decent abilities. Amusing.