Blaring horn intro on "Two Lovers" definitely floats my boat (as does the "Canadian Sunset" intro on "My Guy"). Buckinghams....impressive enough intro on "Drag", but my vote for their stuff would be a tossup between the intro "I've Been Wrong Before" or their cover of James Brown's "I'll Go Crazy".
And if we're talking about Chicago/Midwest regional stuff, how about the Five Emprees' "Little Miss Sad" or the Mauds "Soul Drippin'"....or up to Minneapolis for Crow's "Evil Woman (Don't Play Your Games with Me").
Or perhaps the most unique intro for a group from the Midwest (or anywhere else, for that matter), would from The Novas of Madison, WI on "Do The Crusher" from 1960....a spoof of TV wrestling.