@Background Pony #8EE5  
CHALLENGE ACCEPTED!

@Miss Shy  
I want to be a tickle-pet, that sounds fun
 
Anyway, either AJ or RD would be cute. Anypony with a reputation for being tough that would melt away in a flood of giggles

@Caroo
 
Hmm, personally I think Rarity would make the best tickle-pet of all. Sure, she ACTS all prim and proper for public consumption, and would loudly protest at anything as foalish as being tickled…but would slowly crumble into helpless squirming and giggling once her flanks or hooves were tickle-teased for long enough, as she secretly misses her days as a filly who got tickled silly by her parents, back before she created this upper-class public persona. :)

For my money, I’d pick Twilight and Fluttershy.
 
Yeah, I’d risk being thrown into a wall, but Twilight’s been shown to have quite a lot of tickling resistance, and is the only one in-show to not instantly break out in laughter upon being tickled. It would be interesting to see what it would take to break her, provided I can disable her magic somehow.
 
Fluttershy just seems like she would be extremely ticklish, and it would be nice to be gentle with her, more of a teasing and playful time.

@Breakdown  
*too
 
Dammit!

@Background Pony  
Honestly, a fetish like this is so very mild when comparable to everything else. Also, normal people can be normal and still HAVE fetishes. You’ve probably been to very dark cesspits of the internet if all fetishist’s you’ve encountered were as incoherent as mentioned.

@Background Pony  
Welcome to Derpibooru, man.

Holy shit you guys are the most literate people I’ve ever seen to describe something so fetish-y

OMG! MOAR!

@Miss Shy  
Why not tickle every stallion, mare, and foal in Equestria!!

@Miss Shy
 
That’s a difficult choice. I’m caught between the two for a few reasons:
 
I consider myself a sadist, and would take great pleasure in pushing Rainbow Dash past her limits. If she loses it with just a teeny feather, one can only imagine how she would react to more devious tools employed on her overly sensitive soles.
 
Applejack, on the other hand, would be my choice for the same reason. Watching her resist my methods, fighting with everything to keep from giving me a single laugh, and then the satisfying feeling of breaking her into giving in. But it doesn’t stop there. After gaining the laughter, I would take her to the limit as well, to the point where the stoic tomboy becomes the helpless and hysterical schoolgirl.

Rainbow Dash sounds like the more fun one to tickle.

dARN RAINBOW

@Miss Shy  
Applejack hands down, I’m rather fond of the tough ones who resist >.>; And you can’t go wrong with a farm girl.  
Twilight would also be on my list as well as Pinkie though outside of the 2 choices however.

Lovely

@Caroo  
Dude, this is Miss Shy you’re talking to. Best be careful that you don’t accidentally get her off. ;)

@Miss Shy
 
For my money, and how I view the ticklishness of the mane 6 in my mind. Here’s my preference:
 
1: Twilight Sparkle - Moderately ticklish pretty much all over. But being a lovable little egghead, I bet being teased so playfully would excite her.
 
2: Applejack: She’s gonna be a tough girl to get laughing, let alone begging. But she will let you try.
 
3: Rainbow Dash: Super ticklish and hardly able to stand it. But make it a test to her ego and she’ll try to withstand the teasing tickle torture the most!
 
4: Fluttershy: Hmmm..hard to say how she’d react. Makes me wonder.
 
5: Pinkie Pie: She’d of course be very ticklish, but she’d also see it as fun. Be just as likely to try and get you back the moment you stop.
 
6: Rarity: I don’t know if such a proper pony would even enjoy being tickled.

@Miss Shy  
Between the two: AJ.  
Even the great and powerful Trixie knows that AJ is the one to pick for a tickle pet! I’d have to agree with her:  

 
 
Would not pick Twilight for a tickle pet…  

@Miss Shy  
@sunnysurfer101ma  
Wrong answer, all of you. Correct answer is Vinyl Scratch. You all failed the test.

@Miss Shy  
Applejack would have the nicest legs as anthro or humanized, thus apple-bucking thighs.
 
AJ.

@Miss Shy  
……..Can I cheat and Pick both RD, AND Twilight?

So which one would you choose as a tickle pet?
 
Rainbow Dash, the athlete who’s so ticklish, she’s a giggling mess in almost no time, with almost no effort, providing hours of entertainment as you lightly tickle her? She would struggle in her bonds, screaming and cursing and trying to escape. But what she doesn’t know is that this is simply the opening, and you’ll make her laugh like she could never believe
 
Or Applejack, the tough farm girl who’s stubborn and hard to break, but when she does, she has a loud laugh? Every time you make her surrender to tickling, it’s always satisfying to have her plead and beg immediately as her toes splay, making it easy to get her weak spot, where she almost instantly goes into tears.

You know what? I hope nobody tags this as foot fetish. Nothing really hardcore is going on.