Ah, the ultimate casual card that pays homage to the Alpha days of Plague Rats.
[Decklist] Restless Rats Syndrome
20 Relentless Rats
The Boring Stuff
4 Maelstrom Pulse
4 Dark Ritual
The Fun Stuff
3 Bloodbond March
4 Desperate Research
1 Locket of Yesterdays
2 Echoing Courage
1 Thrumming Stone
The Other Stuff
2 Buried Alive
4 Overgrown Tomb
Ah, a deck with a bunch of cards you wouldn't use in any other deck -- my favorite kind of deck.
You knew the moment you laid eyes on Relentless Rats you knew you had to make a deck around it. Many have valiantly tried. Many more have failed. And this deck? Marginally better than most, I'd wager, but it'll still lose you more games that it wins.
It's slow. It's deliberate. And most of all, it's predictable.
The rats themselves need no introduction, but it should be noted that I intentionally included 20 copies in the deck. "My deck is one-third Relentless Rats!" you'll say with pride. The rest of the deck just piles on the funny. Desperate Research to keep the rats coming. (It's not rare to grab 4 or 5 of them in a single draw.) A single Locket just because besides The March, no other card in the deck would benefit from more than one copy in play. It's tempting to add more, but it's really not necessary. Using Echoing Courage is a common tactic to abuse token creatures. But when it's the rats, it's especially satisfying.
Marrow-Gnawer is more of a "Win More" card. It's tempting to add more copies but he has a lot going against him. He's 5cc, he's just a 2/3 creature, he's legendary, and you have to sacrifice your Relentless Rats to get him going (weakening the rest of the rats). He can still pull his weight if his Fear will put you over the top in a stale mate, but he's usually not very necessary to win. (But still fun.)
The real show stopper are the Bloodbond Marches. It gives the deck lasting ability that just won't let up until either you win or they win.
Thrumming Stone deserves an honorable mention just because you can essentially Ripple through your entire deck, possibly casting all 20 rats in one fell swoop. The problem is that it's a little slow, and unlike The Marches, it's a all or nothing deal.
Last, but not least, we have the new Maelstrom Pulse from Alara Reborn. In the past, I've always had problems adding control. This is a slow deck to begin with, so omitting control completely isn't really an option. You've probably tried this yourself in your versions of the deck and... it just sucks. I've tried a combination of Duress, Naturalize, and Chainer's Edict in the past, but the problem was that it kept on eating into the Relentless Rats total. (No fun.) With Maelstrom Pulse, it's an all-in-one fix it card, of the correct colors, that works in a pinch. If you're really desperate for it when something on the board is bothering you, you could always Desperate Research for one and hope you get lucky. And guess what? It fits thematically! Sure, you'd never Maelstrom your rats away intentionally, but you could if you wanted to, and that's good enough for me.
That's all folks.
Happy hunting and you're welcome.