I like writing spells for standard GURPS Magic. My players tend to as well, so I've got quite a few of them saved up. Here's one I've been working on: it's a Blocking spell for Light and Darkness since that College lacks one and I think it could use at least one. I'm not sure about the energy cost, though since this probably isn't any better than Iron Arm I don't think I would want it to cost any more than 1.
Light and Darkness
The caster interrupts a melee attack with a brilliant flash of light at the attacker. This counts as a Parry. The subject resists with HT; if he fails to resist he is blinded for 3 seconds and his attack misses. If the subject resists, but his margin of victory is less than 5, he is at -3 to DX for 1 minute, including for this attack.
The Bright Vision spell resists. The Protected Vision advantage and other such appropriate measures give their normal bonus to this resistance roll.