There was the tip of a headphone plug stuck in the audio jack of my boss's iPhone 4. The internet suggested that he put a dab of super glue on the end of a q-tip, put the tip of the q-tip into the jack, and remove the broken tip once it was glued to the q-tip. This just resulted in an audio jack full of super glue.
Fantastically! I followed the ifixit guide "Installing iPhone 4 Headphone Jack & Volume Control Cable" found here iPhone 4 Kabel zu Kopfhörerbuchse/Lautstärkeregelung austauschen and had absolutely no problems at all. I really should've taken some photos, as I am rather proud that a repair project of this nature went off without a hitch. The plastic opening tools were extremely useful and worth every penny. The tweezers were nice to have on hand but not entirely necessary except, possibly, for steps 25 and 26. Having a good set of really small screwdrivers was also completely necessary. If I didn't already have some, the repair would've been impossible.
The screws are really really tiny. I took a piece of blue painter's masking tape and wrapped it sticky side up around a small 2x4 block. I then put the screws head down on the tape in clusters matching the configuration that I removed them so that they didn't get lost. During reassembly, having the screws ready and laid out with the correct screws matching the correct holes was extremely helpful.