GURPSよろず

Many physical 有利な特徴 represent body parts, including 「爪」, 追加の腕、追加の脚、追加の口、眼球防護膜、とげ, 「攻撃部位」, and 「歯」. These are “always on” by default, whether they’re due to racial makeup, genetic engineering, implants, or super-mutation. The GM may permit shapeshifters and those with retractable implants to add Switchable (+10%), however.
Not every option is immediately obvious. Some changes are subtle, such as being able to darken the eyes to gain Protected Vision. Others involve body parts implied by a special modifier; e.g., Doesn’t Breathe (Gills, -50%) and 「飛行」 (Winged, -25%). A few even represent the absence of a body part, like switchable Payload as the ability to create a new body cavity.
Be creative!

■Alternatives
　For those who can transform into almost anything, Morph (see 「形態変更」, p. 74) is more economical --and flexible --than many individual body parts with Switchable. The same is true of 「モジュール式能力」 (p. 62) with Physical and Limited, Body Parts Only.

■Powering Up
　Switchable body parts suit divine powers bestowed by beastly or monstrous deities, especially if transformation into a full likeness of the god is sacrilegious; e.g., the Tiger God might grant switchable 「爪」 and 「歯」, but not permit 「変身」 (Tiger).
Body-alteration and animal-related powers frequently include similar abilities.
才能 benefits HT rolls to avoid or recover from crippling of the body parts, and DX rolls tied to extending or retracting them (e.g., to reach something or escape from bonds). It doesn’t affect attack rolls for added limbs, 「攻撃部位」s, etc.