I wondered if anyone had played in a game where the PCs had permanent symbols (e.g. pain, fear, persuasion) inscribed on their shields, armour, etc? If so, were these powerful effects, or not worth the money/XP?
I've done it as a GM. It can be powerful, but it's really really deadly to anything low-HD in the vicinity. I'd probably try to have shield coverings and such so I could have the symbols NOT affect my mounts, servants, friends, and informants. Of course, shield covers are probably easy to destroy in combat....
It would really blow up summoned creatures around you as well. Make sure you coordinate with everyone else on this.
And your GM will have every legitimate excuse to screw you. Carrying around an active symbol is sort of like walking around town with an armed nuke strapped to your forehead. What happens if a pickpocket lifts your shield cover in the marketplace? Or if you have to take the cover off to repair the shield after someone tries to sunder it? Or if you roll a nat 1 against a fireball and the cover burns off?
Same thing applies to other ways of carrying symbols around, though the specifics might differ. There is often a very good chance that the thing will go off when you don't want it to, and destroying the item it's on will probably destroy the symbol as well. You can exclude some people from the area of effect when you cast it, but what if you make new friends later on?