In my opinion, the leading contenders for best MRs are:
Best Mileage Runs:
(Demonstrates the ART of MRing, no mistakes,Extra routings, or bumps considered.)
Latin Pass 1,000,000 bonus Jan-July 2000 ~$3000
dhacker
Air Canada 6X bonus, January 1988, C$40-50 --> 9600 miles
Oreck
Star Alliance 5th aniversary 2002 ~500,000 miles for ~$2000
satori
Swiss segment promos - some yeilding 0.002 € per mile
Alaska 100,000 bonus for 35 segs 2003 ~150,000 miles for ~$1000
Seat 2A
Some of the Best Status Runs Ever:
2003-4 CMB-SIN-ICN-LAX-SFO RT on OZ in F ~$2900 then yielded ~60,000 LH status miles
2002?
The TG BAHT Run UA 1K Status for ~$750
Some of the best Mistakes:
(Bookers posses the excellent ability to pounce on a mistakes when they happen)
~$200 AZ DEL-LHR Business Class
~$200 AZ YYZ-LCA Business Class
~$40 LEB-ART
~$40 US CLT-LAS
~$120 BA US-Europe WT+
~$100 PHX-CDG
~$150 AA LGW-CLE
~$200 BA LHR-HKG
~$300 BA DEL-LHR-SYD First Class
~$200 BD MAN-CHI E+