1. PETG

Poly Ethylene-Glycol, and other similar co-polyesters are all suited greatly for 3D printing prints for outdoor use. PETG is naturally UV resistant. Its tensile strength is almost as good as ABS, but it is much easier to print with due to lower printing temperatures. It is also a recyclable and biodegradable plastic, unlike ABS and ASA.
While PETG may demonstrate some discoloration over time under direct sunlight, that is about the extent of damage that the sun would cause to PETG parts. 

2. ASA

ASA (Acrylonitrile Styrene Acrylate) is similar in mechanical as well as general properties to ABS (Acrylonitrile Butadiene Styrene), with one major exception: UV resistance. ASA can withstand UV exposure much better than ABS. As such, it can be used to print parts or objects to be used in direct sunlight, rain, and wind without any issues like increased deterioration or intense discoloration (only true for pure, non-coloured ASA).

ASA is considered to be slightly trickier to print with than ABS. But if your part needs to bear the sun all day, the extra effort would pay off by the assurance of a longer lasting and more reliable print.

3. Polycarbonate  

On most 3D printers, polycarbonate (PC) is considered to be a pain to print with. This is mostly due to how differently PC behaves compared to PLA or even ABS during extrusion. PC is an extremely durable plastic. Its tensile strength and mechanical endurance put even ABS to shame. It is also naturally UV resistant, which makes it a prime candidate for printing strong all-weather functional 3D prints.

4. TPE

Thermoplastic Elastomer or TPE can also be safely used in sunlight and outdoor conditions. TPE is also recyclable and environmentally friendly. It is best known for its rubber-like properties. Normally, only higher-end 3D printers will produce useable TPE 3D prints though. So, don’t be surprised if a DIY printer requires some major tinkering before printing with TPE.

5. ABS

Purchase ABS
ABS  withstands the heat, but yellows when exposed to the sun’s UV rays over time.

If you don’t care about the color, or if you are finishing the 3D print by painting it, ABS would still be a viable choice. Although, the other materials are a little bit more easy to 3D print with a smaller risk of warping.

ASA

ABS have a reasonably high glass transition temperature as compared with PLA. UV degradation is also not as pronounced as it is on PLA. ABS is also well-known for its mechanical properties as an engineering-grade plastic.

One aspect that ABS parts cannot seem to escape however, is the discoloration. ABS is notorious for its yellowing over time. This yellowing is exacerbated and accelerated in direct sunlight due to the direct UV light exposure.

ABS also lose its structural strength with UV degradation. So, it is more suited for prints that will only occasionally be used in direct sunlight or would mostly sit in at least a somewhat shaded area.