Write down your memories of the biggest chokes,my "favourite" is sadly Micke Pernfors-Jimmy Connors in R16 Wimbledon 1987.
Micke had 6-1 6-1 4-1(!) and lost,howabout that?
Very similar match at Roland Garros 2003:
Varlet served for the match at 6-1 6-1 5:2 against Nieminen and lost 6-1 6-1 6-7 2-6 4-6.
Also spectacular choke was in US Open 1993 in the 4th round. Well serving Jamie Morgan had 5:0 in the 5th set and lost to Masur 6-3 6-4 3-6 4-6 5-7.
Todd Martin on the Wimbledon's Central Court lost twice having double break in the fifth set (Washington, Agassi) what is also something special knowing how good service player was Martin.