I go to Junior's (aka Cozy's) for the awesome thin burgers. I love that I can request cheddar cheese on them, and they are the only place in Champaign that sell this style of delicious thin burger; they are made to order, so you know you won't be sinking your teeth into a cold slab of meat when you go here. I'm not a fan of the crinkle fries, but this place does slap together a good horseshoe.
I honestly can't tell any difference between the cold fudge custard sundae here and at Jarling's Custard Cup (my guess would be the absence of waffle bowls, which is the only reason I'd go to Jarling's instead)--it's a wonderful chocolate overload and always leaves me more than satisfied. Also, unlike Jarling's, Junior's is open year-round and can meet your sweet-tooth needs any time.
If you're like me and prefer old-style thin burgers as opposed to bloated donut-sized heaps of beef, Junior's is your hook-up in Champaign-Urbana.