Let's be honest about this, it was more like a "straw that broke the camel's back" situation.
The favorite food of choice for Bob and George is/was ice cream. Well that, and beer. Many of the sub/fancomics got their own, too. One even went so far as to name the comic after it.
A handful of these exist in Charby the Vampirate: Charby likes chicken, Mye loves gummy bears, Crispo is obsessed with nachos, Biscut named itself after its favorite food and Breck compulsively shovels down muffins if there are any in front of him. Menu will eat anything.
Human Xykon is shown in Start Of Darkness to enjoy coffee—specifically godawful coffee, which forces his brain to relive every great cup of coffee he's ever had. Discovering he can no longer drink it after becoming a lich makes him a little bit upset.
The hobgoblins' love for Gouda cheese is referred to a few times.
The Monster in the Darkness will eat pretty much anything (except babies, and that includes veal), but his favorite of all foods is stew. Stew is Serious Business for the Mit D.
The now-defunct ROOMIES had Flinters and mints (or anything mint-flavored) and Alex and toast.
Black Mage of 8-Bit Theater also likes pie. Specifically, evil pie.
Schlock Mercenary's eponymous character is fond of a drink mix called "Ovalkwik." The ingredient list is here.
Ch'Vorthq: "Sergeant, you will be drinking a very heavy stimulant cocktail cut with shampoo and high-tensile inert carbon."
Schlock: "I don't drink it, I eat it straight."
Ch'Vorthq: "And I suspect you're addicted to it."
Schlock: (aims plasgun) "Step away from the tub of happiness."
The cast of Schlock Mercenary are also fond of the noble 'Chupaqueso', which is, effectively, melted cheese, wrapped in fried cheese, traditionally garnished with cheese. It's not a good food for a prolonged lifespan, but mercenaries don't tend to live that long anyway.
Doc of The Whiteboard enjoys Mountain Dew so much, he brews his own extra-potent blend. He also uses Dew to brew coffee.
The title character of Weesh recharges his powers by eating licorice.
The Cubi race in Dan and Mab's Furry Adventures scores double. They don't actually need to eat regular food and feed off emotions instead, and each Cubi has a favourite emotion. However, they can eat for pleasure, and typically eat nothing but one or two favourites. Of the main cast:
Fa'Lina seems to have a thing for muffins.
Dan loves ale and according to his sister has eaten almost nothing else in the last three years.
Abel is unusual for a Cubi, in that he eats regularly and eats a range of foods.
In Teh Gladiators, guest gladiator Leeroy Jenkins (of World of Warcraft fame) is seldom seen without his crab cakes. Made doubly funny because, in the actual game, crab cakes are a very low level food that would take an entire stack and several minutes to bring a max level character back to full health. True to this, the one time he actually fights on the heroes' side, he doesn't finish eating and get up to attack until after the battle is over.
Ricky from Ratfist loves chili. No, maybe you're not understanding here: Ricky loves chili. He finds a bowl of fresh chili, preparednote almost exactly the way he likes it, in the middle of the street. So he eats it. Bonus points: It was left there by his ex-boss, who mixed in a little cat feces because he needed to infect Ricky with Toxoplamosis gondii.
A statistically absurd number of characters in Irregular Webcomic! describe frozen yoghurt as the best thing ever. Curiously, this does not include the resident Big Eater, Professor North Dakota Jones, whose favourite food is "whatever's pricey, yet available in large quantities". With someone else paying.
Shortpacked!: Robin and anything sugary, given that it catalyzes her Super Speed. Two specific items are more associated with her than others, however: Skittles, which she's often been told she smells like; and Cadbury Cream Egg cerealnote really just Cadbury eggs in a bowl with milk, which gets her so hyper that she blacks out for long stretches of time as she causes increasingly absurd things to happen.
The titular Modest Medusa loves Chocodiles (chocolate-covered Twinkies).
Halo of Grrl Power loves spicy food — so spicy, one restaurant makes her sign a waiver.
Amethyst Lashiec, from Heartcore, absolutely loves barbeque sauce, such that she'll drink it straight out of the bottle.
Her father, Royce, loves fancy foods in general ("Cuisine" being listed as his muse), but seems to like birthday cakes so much that he not only has one every day, but the theft of said cake is considered grand theft and a capital offense.
In Polandball, each country has its stereotypical national dish as a favourite. They're even fond of repeating the names of their favourite food in random background dialogue, or use other countries' favourites as racist slurs. Especially common ones are Turkey with kebab, Great Britain with tea, and the USA with burgers.
In Hyperbole and a Half, Allie's was mistaken for hot sauce for years due to an attempt to impress a family member. She was not pleased by this, especially when she got sets of hot sauce for Christmas instead of toys.