I'll cut to the chase: the Ostrichpillow Eye Mask is the best I've tried. It's made from plush 3D moulded foam that sits flush to the contours of your face, which is both seriously comfy, and excellent at blocking all the light out. It doesn't press against your eyes to achieve that total blackout either: the eye cups are moulded outwards, so you can easily open your eyes while wearing it. Which is an entirely more pleasant situation for sleeping.
You can pick one up for GBP £38 / USD $45 / AUD $66 direct from Ostrichpillow. That slightly higher price is, in my opinion, well worth it if you're a sensitive sleeper... or need to buy a Christmas gift for someone who is.
If the name is ringing a bell, this is the same company that brought us that bizarre 'Napping Pillow' you pull over your head when you fancy a daytime doze. Honestly, weird looks aside, I'm on board with that design too.
The eye mask is going to get you fewer funny looks around the Christmas tree though, so let's get back to that. The design comprises six layers that balance thickness, density and cushiony softness to deliver a comfy, breathable, blackout experience. The moulding is designed to work for a wide variety of face shapes and sizes, and a thick, easily adjustable head strap keeps it securely in place all night. Finally, it's completely machine washable, and comes with a handy storage and transport pouch. There's a 100 day returns period and 2 year warranty for added peace of mind.