So you bought yourself a 3D Printer, maybe a PrintrBot Simple Metal like I did, and you want to get started taking over the world with your mad printing skills. Before you do, however, I've made a list of tools that I think can make your daily life with a 3D-printer a lot easier...
Step 1: Masking Tape
By far the most important thing to buy for your 3D printer is masking tape. By carefully putting strips of masking tape onto your printer's bed, you not only help the printed object adhere to the bed a lot better, you also make removing the completed object from the bed a lot easier, and protect your bed from damages.
To make life easier and have fewer overlaps of tape (where potentially print height will differ) use as wide a tape as possible. From what I know 50mm is the widest available.
Don't be cheap
Masking tape is important, so don't buy the cheap stuff. I like the tesa-brand, but basically what you want is the one with the strongest adhesive. Usually you will see people selling blue masking tape, which is UV-resistant. I've personally never tried it, the yellow stuff works fine for me.
Step 2: Glue Stick
Ever had a 3D-print go horribly wrong because of warping? Yeah me too, but I've found that using a glue stick to add a layer of glue on top of the masking tape right before printing makes the print adhere much better to the bed. Again, be careful not to buy to cheap glue, though they're usually pretty cheap in general. I use the Pritt-brand, which is supposed to be good. Just be sure it adheres to plastic!
Step 3: Tweezers and Pliers
If you've followed the last two steps you might have experienced how well adhesives work in making your object stick to the printer bed. But unfortunately this might also also mean having trouble getting your printed object off the platform. Introducing tweezers and pliers. Get a few different ones for different sizes of objects. I mostly use the small tweezers and the big poly grip pliers. As an added bonus the small tweezers are also great for removing any filament that might ooze out of the extruder pre-printing.
Step 4: Caliper
By entering the world of 3D-printing, like it or not, you're also entering the world of engineering. Get a caliper to make sure your prints have the correct size, but if you're designing your own objects too, use it as great way of dimensioning parts of your object. I've bought a digital one, which is a bit expensive, but it gives you two decimals of precision which is really nice when you want to measure the true diameter of your filament or how much your PLA shrinks during printing.
Step 5: DIY Hot End Cleaner
I never had this problem when I worked with a MakerBot 2, but before I adjusted my PrintrBot filament settings to 1.80 (even though my filament is supposedly 1.75mm), I had a lot of problems with my hot end clogging. To remedy the problem I filed a thin needle using a Dremel until it had a diameter less than the 0.4mm hole that the hot end features (hey, what a great way to use your new caliper!).
Drive your filed needle carefully through your heated hot end to unclog it. The roughness of the filing makes the plastic adhere to the needle better. WARNING: Be careful when you drive anything through your hot end. You can damage the hot end which will really mess up your printing.
For increased usability I added some hand-molded plastics (Polycaprolactone aka. Polymorph) for a handle.
UPDATE: Thanks to ark19 for suggesting using acupuncture needles instead. These can be purchased in different sizes to fit your nozzle.
Step 6: Silica Gel (for PLA Users)
If you're printing using PLA plastic, buy yourself some Silica Gel, or even better, don't throw out the packs that most likely were included when you bought your printer or filament. PLA absorbs water over time, which can results in bubbly printing, so do yourself a favor and store your filament in a closed plastic bag with a few packs of Silica Gel. You can buy 100 packs on eBay for around $1-2 including delivery, so there's no excuse not to!
Step 7: The End
There you go, some tools which should make it easier to print and enable you to spend time on what's really fun to do with a 3D-printer: printing!
Let me know if you have any questions, comments, or suggestions for additional tools or brands.