Do you use "mascot" cards?

[Strawberry Dwarf]

I do, sometimes.

Mascot is a sub-standard or obsolete creature card. Just 1 in main or SB - sided-in in unwinnable matches.

Some typical examples:
Pearled Unicorn
Ironroot Treefolk
Dwarven Warriors
Scavenging Scarab
Storm Crow
Coiled Tinviper
etc.

Surprisingly, it works sometimes out of pure luck. Also, there is the WTF factor: opponent can't believe what he is playing against and feels uncomfortable about possible loss.

[thecrav]

I play a Library of Leng or Lhurgoyf in almost every Vintage deck I build.

[H]

Surprisingly, it works sometimes out of pure luck. Also, there is the WTF factor: opponent can't believe what he is playing against and feels uncomfortable about possible loss.

Well, I'm pretty sure LSV often does this sort of thing. Includes a couple "fun-ofs" in the sideboard, to catch people off guard.

You'd honestly probably do a good bit better by including "more objectively powerful" cards instead. So, a 3 mana 2/2 might win a game, but really a 2 mana 2/2 would likely do even better, in this case. I don't really think it's too much that Pearled Unicorn is really "worth" running, just that a 3 mana creature might happen to be what the doctor ordered. Honestly, think of what might happen if it was something like Aven Mindcensor, or something else that just might happen to randomly hose an opponent.

[Megadeus]

I've run more than my fair share of Giant Solifuge in Maverick/Nic Fit decks. Also got top 8 of an open with a Stillmoon Cavalier in deadguy once, but that was just because I wanted a man who could block Griselbrand, Marit Lage, and hoses DnT.

[H]

I've run more than my fair share of Giant Solifuge in Maverick/Nic Fit decks. Also got top 8 of an open with a Stillmoon Cavalier in deadguy once, but that was just because I wanted a man who could block Griselbrand, Marit Lage, and hoses DnT.

Yeah, I mean, "the man plan" or "rando-dudes" often just works because bodies do things, where situational spells often might do nothing at all. In this sense though, indeed, "random dude" is likely better off not being "I literally hit random on gatherer" and like you say, a creature with actual game-wise "upside."

When our meta was slanted toward Blue, I'd often toss a Thrun, the Last Troll in my sideboard and randomly win games with it. But, later the printing of TNN meant more people were playing things like Edict. But before that the card would win sometimes just on the merit of being totally not what anyone realistically was expecting.

[Mr. Safety]

I've run more than my fair share of Giant Solifuge in Maverick/Nic Fit decks. Also got top 8 of an open with a Stillmoon Cavalier in deadguy once, but that was just because I wanted a man who could block Griselbrand, Marit Lage, and hoses DnT.

That's awesome! Both of those cards have captivated me in the past. When modern first started I did a Deadguy-ish deck with Stillmoon + Sword of Fired and Ice + Quest for the Holy Relic. Protection from everything but green! Giant Solifuge is just a monster, the only thing outclassing it is Thrun (which doesn't see any play anymore, sadly.) I like the cut of your jib.

[Michael Keller]

I've won blue dual lands in multiple tournaments with these cards (links to resources):

Polar Kraken (http://www.mtgthesource.com/forums/showthread.php?3996-Reference-Historical-Top-8-up-to-March-08)
Ali from Cairo (http://www.mtgthesource.com/forums/showthread.php?24895-Report-Return-of-the-Living-Dead-3rd-Jupiter-Games-NELC-w-Manaless-Dredge!)
All Hallow's Eve (http://mtgtop8.com/event?e=293&d=117937&f=LE)

Those are my three.

[Begle1]

I'll do this to lower the power level of Commander decks.

Deck too good? Then play a certain number of Frozen Shade, Poultrygeist, Scathe Zombies, Crimson Hellkite, Pearled Unicorn, Bird Maiden, Merfolk of the Pearl Trident, Grizzly Bears, Zephyr Falcon, et cetera.

That way when you combo off or something, people can't complain because you just hold up a Mons's Goblin Raiders or something in response.

In competitive Magic there are cards that I have a particular liking for and play for a while, but only because I think they'll help me win. Especially in Standard; I've gone seasons being the only person I've seen play certain cards. A while ago it was Unsubstantiate and Supreme Will. Now it's Heartless Pillage and Carnival // Carnage.