Former boxer and long time boxing history lover, I have out together a bucnh of great rounds for your perusal:
Marvelous Marvin Hagler vs. Sugar Ray Leonard - Round 9 (1987)
An amazing round in a controversial fight, love this round. How you scored this round was how you scored the fight IMO:
http://youtu.be/G5jUDE9mIXM?t=7m3s
Iran "The Blade" Barkley vs. Thomas "Hit Man" Hearns - Round 3 (1988)
Thomas Hearns had challenger Iran Barkley cut and hurt badly to the body as early as round 1. From NOWHERE Barkley uncorks a right hand in the 3rd round and the fight is over! Saw this live, was shocked:
http://youtu.be/7GBbLUkQn2s?t=12m40s
Roberto Duran vs. Davey Moore - Round 7-8 (1983)
A young and inexperienced champion takes on a living legend and Duran in Madison Square Garden has one of his best nights. Brutal, and the crowd loves Duran even though Moore is from the Bronx::
http://youtu.be/yGTlQsjzmWU?t=20m50s
Roberto Duran vs. Iran Barkley - Round 11 (1989)
Ok, so you have seen both Duran and Barkley, but how about against each other?
Considered finished and washed up (again) Duran summons one of his best fights and takes the title away from Barkley largely on a wonderful 11th round. What a combination to put Barkley down, and again, the crowd (snowed in!) were wild for Duran. Side note, watched this fight snowed in with my Mom live, maybe our best time together:
http://youtu.be/knjh-ucbrKg?t=56m5s
Mike Tyson vs. Tyrell Biggs - Between Rounds 6-7 and Round 7 (1987)
I know Mike Tyson is a joke now, but as a boxing fan (and have seen well over 1000 fights dating back to 1920) I can tell you he was one of the best ever at his prime. Kevin Rooney was his coach and it was amazing. In this section against Biggs you hear Rooney telling Mike "those 7's were beautiful. Now 6-5-1. 6-5-2-1" which is their jargon for punch combos. It's over the next round:
http://youtu.be/LpH7jVPT_Zc?t=27m11s
Enjoy!