Striker is an exotic physical advantage. (B88)
- Limb (arm, leg, wing, striker, or prehensile tail): Injury over HP/2.
"add Sorcery Talent to DX or skill before halving it to determine Parry" is mentioned for Iron Arm in GURPS Sorcery: Protection and Warning Spells. This was never addressed on page 78 of GURPS Powers which skipped from Stretching to Striking ST.
for other advantages
- the Striker only for Enhanced Parry
- Only to reduce penalty for multiple unarmed Striker parries for Trained By A Master
In early days http://www.sjgames.com/gurps/Roleplayer/Roleplayer20/Gimme-a-Hand.html it was a -1 to cost per -1 to DX to aim, effectively creating free strikers. The change to the limitation system in later editions fixed this.
http://forums.sjgames.com/showpost.php?p=726722&postcount=4 says weight is ST/10
- Strikers do not function as arms.¹ They're effectively weapons that don't take damage. That's a gross simplification, but it's how they work. An upshot of this is that attacks with Strikers don't hurt the user. This includes slams – and as B372 says for shield rushes and p. 122 of Martial Arts says for slams with weapons, when you use a weapon to slam, it takes the damage for you. Since Strikers can't be damaged . . . it's always safe to slam with one.²
https://web.archive.org/web/20180122220017/http://forums.sjgames.com/showthread.php?t=131561 Toptomcat does good analysis of drawbacks of Limb, Shin