Caffeine is my first go-to drug for creativity. A cup of coffee wakes me up and makes me outgoing, but get bit of espresso in my system and a chorus of angels will sing poetry out of my cock. This is my bread and butter, and at the height of my use I have to wean myself off from >4 shots a dose just to step back. Currently I need at least one a day or I hate everything. I just brewed two in a new machine with new grounds and I'm scrounging the net for inspiration.
Weed is good for brainstorming and getting in touch with the right train of thought, but when I've had enough for a good idea I'm usually too sedated to bother using it constructively. I've never successfully combined it with coffee for the purpose of removing this impediment.
LSD has great potential as a catalyst in the long term, post-integration period for several months after tripping. There's this surreal quality where I'll find myself in an immersive state of mind that produces interesting concepts in a narrative fashion, ripe for the picking, but the catch is that it's more difficult to remove myself from this and I'll often resort to meditation and other low-stimulation activities to calm my thoughts and regain focus.