1. Flashark.com : Definately brandable if we put it as FlaShark.com. Perhaps u forgot to write it that way.
Agressive flash game/presentation/animation development company can pick it up for a good cost, depends on your negotiation power.
They would try to launch it as brand or name their company as FlaShark.com
Good scope! All the best dude
2. ProductsMarket.com : Easy to remember but could have been better if singular(can get good returns if developed)
If you offer a service allowing users to create their online shop for free this can work.
Try buying singular version of the domain then u might be in top position to call on your shots.
3. Sectarismo.com : Tough to spell & to remember, not a good idea to buy or to develope it.
Sorry dude bad one.