What about incorporating special cheeses or spices?

Zest of any citrus fruit will go a long way.

My grandmother would always put almond paste into her tarte crusts. Which wouldn't work for you, but gave me the idea for flavoured extracts such as lemon, chocolate, etc. Dried fruits would work well if integrated with a food processor. For savory crusts, thyme or rosemary is never a bad choice and for sweet, a little molasses or candied ginger would be nice too.

I am also quite fond of poppy seeds in tarte crusts.

One of my favorites is for a key lime pie my dad makes. Rather than using the traditional graham crust he uses crushed gingers snaps instead. He treats it the same without pre-baking. I find that this crust gives the pie a bit more pizazz. I have to agree with joe that zest always works well, and there is always the possibility of trying a more substantial crust depending on what your using it for. For instance if I'm making a fruit tart I may go with a more cake based crust depending on what I'm filling my tart with. Its spongy and for me makes the tart feel more decadent sort of like tiramisu.

Citrus zest and an extract of some sort will also give the crust greater depth and flavor.

Use a differnt fat, particularly an animal fat. Duck, goose, bacon, chicken -- you get the drift.

Sometimes, i'll either add or swap out some of the salt and/or sugar for stuff with lager crystals (i.e. coarse sea salt and demerara sugar). I think those large bits work well to reinforce existing flavors and keep the taste-buds guessing.

The first thing I thought of was coconut. That might be yummy!

My go-to would be citrus zest, as others suggested.
How about crystallized ginger (chopped finely)?

Wasn't there a recipe here recently that incorporated dates in the crumb crust?

I second Bobette's father's use of gingersnaps and would suggest looking for other stiff cookies to try. A small amount of pretzels added to your graham crackers would also add pizazz.

Yes, nut allergies here, too!
I have used as main ingredient for crumb crusts: safe pretzels (bachman is our go-to brand, as is rolled gold brand---check your labels), ritz-type crackers, plain or vanilla oreos sans icing, homemade granola, wheaties, shredded wheat, grahams, safe cake mix & oatmeal combo. White or brown sugar to taste if needed, a fat such as butter, lard, or stick margerine to bind. A touch of cinnamon or nutmeg if it compliments your recipe is a nice touch. Have fun experimenting, you just need a starch, a sweetener, and a fat.

I guess my first thought was to incorporate some different types of flours, various non-wheat grains and/or textures (maybe coarse ground?). I know this doesn't necessarily help with cracker crusts, but for other types it might work.

Just a little recommendation from a pastry chef-in-training: use flavored *oils* rather than extract....for example: lemon, lime, and orange oils made by Boyajian are far superior in flavor to extracts, and are a worthwhile investment as you only use a few drops per recipe. Happy baking!

I have used cookie crumbs (like graham crackers) instead of flour to roll out standard pie dough, so the crumbs are imbedded in the crust. Really good with a chocolate custard or pumpkin pie...

I saw a "raw" "cheesecake" that incorporated dates into the crust mixture, which also involved almond meal, but it would probably work well with crumbled crackers or cookies.

I love 1790 House's idea for brown sugar. You could also brown your butter and cool it before making to get a brown butter pie crust- sort of toasty and caramely.

Nigella Lawson has a recipe for a tart using chocolate pastry, with vanilla cream filling and raspberries. It looks really special.

I am allergic to tree nuts, but can eat pine nuts. Toasted, they are a good replacement for a nutty taste.

i don't know if this counts but i sometimes apply a thin layer of chocolate ganache to the crust before adding in my cheesecake filling. it's just a nice surprise when you cut into it. also, i tend to add a little mint extract to my oreo cookie crust as well. thank you dairy queen for the idea!

Crumble Amaretto cookies in the mix... and you've got Italian Jazz!

True Amaretto cookies do not have almonds, just the pit of Apricots. But, often, in America they make them a little different - so read the ingredient list carefully prior to crumbling!

Well this is pretty simple, but I mistakenly bought cinnamon graham crackers when making a graham cracker crust for my cheesecake. I didn't even realize it till I started grinding them up. It turned out really well and now I can't seem to bring myself to make a graham cracker crust with regular grahams.

I may have to try that ganache idea from above though - that sounds amazing!

For savory pies, like quiche, use left-over cooked rice. Press it into a greased pie plate and bake a little to stiffen it before adding wet ingredients.

Also, for savory, any herbs and spices added would be yummy.

For sweet, I sub. a shortbread cookie dough and bake it before adding wet ingredients.