Guild Wars 2

So say I have my longbow and greatsword equipped. For both of them I have sigil of force applied which grants +5% damage.

So because I have two of them does that mean I have total +10% damage?

I’m not too sure, but I always assumed that the damage of each is related to the skill provided by each weapon

Depends on the type of sigil. Here’s a good explanation.

http://www.reddit.com/r/Guildwars2/comments/10ilke/how_sigils_work/

The sigil(s) of unequipped gear will not affect your character’s performance, just as the rune that’s on your breather only is active when you’re wearing it (underwater)

sigil of force doesnt stack, maybe its a bug but i dont think it will ever be fixed,
some others stack and some share cooldowns, its complicated