Account achievement weapon skins.
You get 1 at 1000, 1 at 2000, 1 at 4000, 1 at 5000, 1 at 7000, 1 at 8000, and 1 at 10000.
In total, you’re currently able to get 7 weapons.
You’ll probably be able to get them all later, if/when they add more rewards.
See: http://wiki.guildwars2.com/wiki/Achievement#Achievement_rewards
My guess would be that it goes a little bit like this:
1000, weapon skin choice
2000, weapon skin choice
3000, armor skin choice
4000, weapon skin choice
5000, weapon skin choice
6000, armor skin choice
etc.
Basically, in the long run, you can probably collect all the skins.
Vella Absconditus | Human Mesmer
Seafarer’s Rest
Seafarer’s Rest