You're walking down the street....

[Mikefrompluto]

Answer to previous two: {Child of Alara} and {Slumbering Dragon}

{Sphinx of the Chimes} or {Phelddagrif}.

[Agarrita80]

Phelddagrif is freaky man ... I pick him! Sphinx looks belevolent.

{Nightmare} or  {Thundermare}

[All-Mana Mania]

Phelddagrif is freaky man ... I pick him! Sphinx looks belevolent.

{Nightmare} or  {Thundermare}

Thundermare

{Grandmother Sengir} or  {Abomination}

[Mikefrompluto]

{Abomination}

{Ad Nauseam} or {Wit's End} (Dissension version.)

[Agarrita80]

 {Wit's End}

{Craterhoof Behemoth} or  {Ruric Thar, the Unbowed}

[Apathy Reactor]

I'd be more afraid of  {Ruric Thar, the Unbowed}, cause the othe would probably not even see me XD

{Sudden Death} or  {Mind Maggots}

[Agarrita80]

I would say {sudden death} . That would freak me the f out.

{Creepy Doll} or   {Stuffy Doll} m13 version

[IntoFire]

Severed legion. Walking hand army? Creepy.
{Child of Alara} or  {Progenitus}

{Child of Alara}.

{Evil Eye of Urborg} or  {Rakdos the Defiler}?

[Gorzo]

Previous 2: Stuffy Doll and Rakdos. I'm the kind of idiot who would be fascinated by the evil eye and probably try to communicate with/approach it. Then it would kill me.

{Radha, Heir to Keld} or {Glissa, the Traitor}? Which scary lady makes you say "Nope!" and run?

[The1337Magician]

Glissa

{Terror} (10th) {Bloodhall Ooze}

[Agarrita80]

I'd say terror, hopefully I can outrun the ooze.

{Bloodline Keeper} or  {Baron Sengir}

[Apathy Reactor]

Bloodline Keeper

{Grave Titan} or  {Geralf's Mindcrusher}

[Agarrita80]

 {Grave Titan} ... Sheer massiveness and he has a big sword too

{Psychatog} or  {Maze Abomination}

[prayos]

{Psychatog}... cause, teeth man.

{Polar Kraken} or {Dryad Militant}

[Silent1236]

{Polar Kraken}.  That thing is huge...

{Macabre Waltz} (yes, they are waltzing down the street at you) or {Viashino Firstblade}