Surprised you with this one, didn't I? (And no, I did not consider Micah Hoffpauir. Here's the rest of the Cubs' all-time No. 6 list. Incidentally, the number 6 apparently didn't mean anything to Hill; he wore 10 different numbers during his career and in his first stint on the North Side, wore No. 34.)
Glenallen Hill was drafted by the Blue Jays out of Santa Cruz high school in California in 1983 and spent six years in the Toronto minors before his major-league debut in 1989. Never a great defender, he bounced around there and with the Indians before he was traded to the Cubs in August 1993 for Candy Maldonado. That was an excellent deal -- Maldonado had been awful for the Cubs and Hill was a distinct improvement.
The Cubs let him go just before spring training began in the strike-shortened year of 1995 and he signed with the Giants and put up a very good year -- .264/.317/.483 with 24 home runs. After three years in San Francisco Hill signed with the Mariners, and he hit well there too -- .290/.332/.521 with 12 home runs in just 74 games. Inexplicably, the Mariners waived him midway through 1998 and the Cubs signed him.
He played well when he did play, but the Cubs couldn't play him fulltime because he really was, by this time, more of a DH. What you really want to see, and the reason I chose Hill, is this:
To this day no one else has done that. While a couple of home runs, one hit by Dave Kingman, one hit by Sammy Sosa, have gone a bit farther down Waveland, there has never been anyone else who's hit a home run that's landed on a Wrigley rooftop.
Hill lasted about another year with the Cubs and then was traded to the Yankees for two guys you've never heard of. If he'd have been a better defensive player or spent his whole career in the American League, he might have hit far more than the 186 homers he wound up with. In any case, he played more years for the Cubs than with any other team and hit his best there, too: .304/.360/.546 with 59 home runs and 167 RBI in 993 plate appearances. Pro-rate that to a 600-PA season and you get 36 homers and 101 RBI.
And one massive shot to a rooftop on Waveland.