Slant 3D's youtube channel uploaded a video where they redesigned the golf tee to be more suitable for FDM 3D printing. They did not upload an STL for the golf tee, so this is my version inspired by their design. 

Features & Design Considerations:

• Designed to be printed laying on its side, allowing for more reliable printing and a more durable final product (due to layer lines being perpendicular to the impact from a golf club).
• Beefier stem than traditional golf tees
• Ribbed design allows for easy insertion into grass while preserving strength
• Circular divot on top is precisely sized to cradle a golf ball
• Fillets smooth out the crevices, increasing strength in high-impact areas and reducing the aggressiveness of overhangs

May I recommend using a biodegradable filament to reduce on plastic litter :) (Please note that PLA isn't quite biodegradable – it's only compostable in industrial composting plants).