What are you looking for in an addon?

It usually depends on what it is, like with weapons/entities its nice to have custom models and sounds on them, but the most important thing I think is make sure its bug tested, I have been working on a swep pack recently and didn't find any major bugs myself, but when I had some other people test it we found a whole bunch some making the weapons completely broken until you rejoin.

you should make some sort of prostitute swep as there are non that i have seen on the gmod store.