For me it's coding "editors", be it terrain editors or texture editors, or both(usually).Pretty much everything involving brushes.
My most frustrating would be lighting grr.
How about you?

I like nice separate chunks of functionality that i get something out of (graphical results etc.)

I dont like when i have to engineer an overly complex algorithm/data structure with an insane looking data flow that then never works and i spend the next week fixing all the logic errors. And then it seems like it works, and i go add an extra feature, and notice its till broken and all my "fixes" were just replacing functioning code with something that hides some other bug somewhere else in the code.

Or something like that.

My favorite part of coding is finding that solution to a weird and obscure bug that's been around for a long time. After already trying to fix it and failing, when you're taking a shower the next day and suddenly, BOOM! You run to the computer, code it up, golden light shines down from above, a choir sings in the background, and you feel like a programming wizard. Until the next bug.

I hate three things: documentation, documentation, and documentation.

After already trying to fix it and failing, when you're taking a shower the next day and suddenly, BOOM!

Man, I can't even count the number of times this has happened. I've started to take showers when i'm stuck on a particularly touch problem just for the fact that for w/e reason I can better work out problems in the shower.

I'm pretty sure if I had a water-proof white board in the shower I would already be a billionaire. :D

I like being able to quickly throw things together and have some sort of immediate feedback.

I don't really like:

writing boilerplate (code that does nothing apart from help glue one thing to another);

having to make changes in a large number of places to add something (such as having to "route" things through a number of unrelated components, *1);

things like array overruns, bad pointers, threads stepping on each others' data, ...;

...

*1: this is presently an issue for most things which have to cross the client/server divide, which often involves fiddling with code in both the client and server parts of the engine, and also with the code for composing and processing the relevant messages, ...

another annoying issue recently has been me not wanting to require 64-bits, but having an engine with enough data (notably voxel terrain) that it doesn't really fit nicely in a 32-bit process (adding the issues of needing to deal more with memory-use management, in-memory compression, ...).