Yahtzee from Zero Punctuation has a nice hat. He goes so far as to mention it in his bio ("a sweet hat and a chip on his shoulder") and draw it on his crude sprite in his reviews.
It's rather unfortunate that he didn't actually wear it the first time he appeared in live-action video, but he has some photos from his visit to Valve, and the next live-action segment featured Yahtzee wearing the hat instead of his microphone headset, communicating entirely in mime. And he says he hates the fans!
As a matter of fact, Trilby, from his adventure game series, the Chzo Mythos, wears the same hat. That's why he's named Trilby - that's what the hat is.
In his review of Metal Gear Solid 4, the sprite's brain pops out at one point... and has a miniature version of the nice hat on it.
He's Tweeted that he doesn't really wear it in public anymore, because it's so nice that it attracts unwanted attention.
Since it originated as an Avatar based forum, Gaia Online has lots of nice hats. Some with eyes, some with teeth, some that are in the shape of rude gestures. Many of them actually have real life counterparts available for sale. (Well, not the rude gesture hat, but most of the other ones). The hats are so iconic, that one of them actually has an enemy based off of in in the MMO.
In the realm of NPCs, the king of Nice Hats is Ian, with his iconic feathered fedora hat. His cat even wears one for a while. After being outed as a vampire (don't ask) and going back to his natural hair color, he ditched the hat. You can craft a replica of it though.
Another makeover has Ian wearing a rather tacky top hat with a feather in it. However, airship captain and resident JerkassCresento has ascended the throne of "King of Nice Hats on Gaia", even going so far as to coordinate a contest for users to submit their own Nice Hat designs.
Also, Homestar's buzzer cap. He wants it to be spun. It makes a whirring sound. And it plays the theme from Night Court. Hilarity Ensues.
The King of Town has a crown that is apparently worth a lot, considering how much it could be ransomed for. Though he may have just bought it at the costume shop.
KoT: Now, despite rumors to the contrary, I did not just buy a crown at the costume palace and ask people to start calling me the King of Town. I earned my title the same way I earned a free combo meal: by purchasing one of equal or lesser value.
Most of the DesuDesBrigade members have nice hats — Professor Otaku wears one both in his avatar and in real life, Arkada occasionally wears a similar one to Kimblee's, JesuOtaku sometimes wears an orange baseball cap, and Malakye has his Zero helmet in his avatar.