I see a lot of people getting scared / killed by creepers. I haven't been killed by a creeper in ages due to my... quick reflexes :3
Basically, whenever I hear a creeper, my instinct is to just run in whatever direction I can, so if I can't avoid damage, I at least reduce it.
On to what scares me in MC. Probably the 2 things that scare me the most is 1) Being in an unlit cave 8000 blocks from spawn on a Factions server (where PVP is enabled), and 2) mining ores at or below layer 11.... because I'm afraid they'll / I'll fall in to lava
"Odd is Benjamin Franklin playing tetherball with Van Helsing. Odd is a big toed tadpole tainted by the tides of a dawn since past. ODD IS A FORTY YEAR OLD OFFICER CRIES HIMSELF TO SLEEP EVERY NIGHT DREAMING ABOUT LIFE ON THE ROAD AS A TRAVELING NAKED CONTORTIONIST! NEVER RETURNING HOME! NEVER STOPPING OR BREAKING HIS STRIDE! Uhm. Unless he sells at TGI Fridays. ******* loves that place."
A couple of things have startled me pretty good. The first new 1.8 map I loaded spawned me right next to three creepers. Luckily I had the good sense to back away quickly, turn around and run. Two sizzled and blew right away, and the one that was a little further away survived and chased me for a short bit. What a welcome to the new version that was!!
There are times when in a cave or mining down a tunnel and it is all quiet except for the block breaking sounds, when all of a sudden I hear a Zombie growl loudly in one ear like it's right there. Hairs on the back of my neck and on my arms stand up and I feel my heart skip a beat!!
The sound of a raging Enderman, and the sound of the beasty in the Spirit World that chases you when you have a Nightmare....What startles me is crouching on high places and feeling your finger start to slip off the shift key, and running into creepers or hearing creepers sizzle when they creep up behind you...especially when you have things stored on your person or chests.
Whenever I play on vanilla singleplayer, I most of the time when it is night, I go adventure. Every single time, a skeleton sneaks up behind me and shoots me, which scares me, because it's unexpected. Then I jump around in real life, then continue.