Merfolk
A Modern deck, by Alloran
29th place at a tournament in Magic Online on 2012-02-19
As reported at http://www.wizards.com/Magic/Digital/MagicOnlineTourn.aspx?x=mtg/digital/magiconline/tourn/3427997

Maindeck:

Artifacts
4 Aether Vial
2 Pithing Needle

Creatures
4 Coralhelm Commander
4 Cursecatcher
4 Lord of Atlantis (Not currently legal in Modern)
1 Merfolk Sovereign
4 Merrow Reejerey
2 Phantasmal Image
4 Silvergill Adept

Instants
4 Mana Leak
4 Spell Pierce

Legendary Creatures
2 Kira, Great Glass-Spinner
1 Sygg, River Cutthroat

Basic Lands
17 Island

Lands
3 Mutavault

Sideboard:
3 Grafdigger's Cage
1 Pithing Needle
2 Torpor Orb
2 Threads of Disloyalty
2 Dismember
3 Negate
2 Vapor Snag