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Anyone who hasn't tried this:

CURRY KETCHUP MIXED WITH MAYO
soooooo wicked.

Bleu Cheese Dressing with a few drops of Hot Sauce

or

Malt Vinegar and Salt

I love truffle aioli! (mayo, fresh ground pepper, few drops of truffle oil.. you can shave a little truffle in if you have the real deal)

Mayo!

mango ketchup, brah'....

Smother them with pulled pork, bbq sauce, and shredded cheese. Yummm...

Heh... spicy cod roe mayo... I liked it at this one place and just last night made my own version... though not cod roe. Equal parts masago and mayo... (well, just mix it until it's about the right color/texture you like)... then dashes of hot sauce... I used Red Devil because I like the vinegary kick to that, but I'm sure tabasco would work. Or sriracha. Here's the tricky part: I kept putting more and more hot sauce and tasting a little but it never tasted that spicy to me. Then I dipped a piece of popcorn (what I had next to me) in it, a little, and whoo boy was it spicy! Something about the mayo keeps it tame until there's something else there, I was really like wha?! I didn't have french fries on hand so I dipped ciabatta (and more popcorn) into and scraped the bowl clean, sooooo good...

(There's an izakaya on St. Mark's Place that does steak fries with spicy cod roe mayo but it's not that spicy, there isn't enough roe, and the steak fries kind of overwhelm the dipping sauce anyway.)

Mmm... I think I'll make more of this today :)

Tartar sauce

in the Netherlands we usually eat fries with mayo, but our special fries are with mayo, curryketchup and raw onions, not mixed into one sauce, but you just sweep the fries through the different sauces. delicious. another one: fries mayo and peanut butter satay sauce! want to try? go check out http://www.pommesfrites.ws/ (2nd ave, NYC): best (Belgium) fries with huge nr of dipping sauces

I almost forgot-- gravy

Buffalo wing sauce

BBQ sauce!!!

Perhaps it's just that we recently celebrated Canada Day an Quebec just celebrated its birthday, but there's nothing like a good poutine. Some fresh cheese curds (squeaky if possible) and some thick gravy. Then you've got yourself a heart attack worth having.