Is it just me, or does that raccoon have the EXACT same mustache as that Samuel Clemens fellow?

Shapeshifters have a tremendous amount of versatility due to the fact that changing their shape also changes their capabilities. In some ways, playing a shapeshifter is like playing two different characters that tag-team the game, which is a bit more complex than playing a standard character with more static abilities. If the complexity doesn't bother you, however, it can be a lot of fun.

Shapeshifter Take an alternate form.
caret-right Drift Some abilities cross over.
caret-right Lapse Forms don't share weaknesses.
caret-right Quickshift Change fast.
caret-right Respec Change size and stats.
caret-right Triplicate Three forms.

Shapeshifter

Utility plus-circleThe Other Me: You have an alternate form which can have access to different abilities. You can change back and forth between your two forms as a procedure. If you want you can designate one of your forms as your “true” self and the other as an alternative, but this isn't mechanically necessary.

plus-circleAlternate Loadout: Both your forms must share all levels and abilities taken in the Shapeshifter archetype, but any other abilities you have learned from different archetypes are temporarily lost when you shapeshift. You can use a keystone to permanently learn a new ability in your second form at any time, up to a total maximum number of abilities equal to your level as normal. Every time you change forms, you lose the abilities of one form while gaining the abilities of the other.

plus-circleVisually Different: Your two forms can look as different or as similar as you please, and can freely cross boundaries such as ethnicity, species, sex, age, life state, or similar. Feel free to customize this according to the exact nature of your shapeshifting ability. Your forms always look like themselves, however- if you have the power to turn into a wolf, then you turn into the same wolf every time.

minus-circleMechanically Similar: Your two forms are both the same size category. You retain the same combat statistics (Melee/Remote/Whelm) in both forms, and any weaknesses you might have are also present when in both forms.

Drift

Utility plus-circleThis, But Also That: Like a werewolf who has an enhanced sense of smell even when in human form, your shapeshifting nature has started to blur the lines between your two selves. Pick two abilities from each of your two forms; you always have access to and may freely use these abilities regardless of which form you're currently in.

plus-circleTriplicate Change: If you also know the Triplicate ability from this archetype, then you choose just one ability from each of your three forms. No matter which form you're in, you can always use all three.

Lapse

Utility plus-circleWeakness Change: Your forms do not need to share weaknesses. If you have a weakness in one form, you don't need to have it when you're in the other. Your different forms can even have different weaknesses if you like.

Quickshift

Utility plus-circleI'm Always Angry: You can change between forms as an action instead of a whole procedure.
caret-right Alternative plus-circleInstant Shift: You can change form at any time as a free action, even when it's not your turn or as an interruption to somebody else's action.

minus-circleAlso Always Hungry: Shapeshifting as a free action costs 1 point of Provisions.

Respec

Utility plus-circleSize Change: Your forms do not need to be the same size- one can be bigger or smaller than the other. Pick different sizes for your different forms when you learn this ability. Remember, the referee can absolutely veto anything really outrageous like turning into a bacterium or a living planet. Don't be that guy.
Utility plus-circleCombat Respec: Your forms do not need to have the same distribution of combat statistics (Melee/Remote/Whelm). Distribute them however you like for each form (just once, though- not every time you shift).

Triplicate

Utility plus-circleThree Forms: Create a third form to go with your current two, with all the same restrictions and advantages as before.