Cricinfo has mentioned MS Dhoni's 93-ball hundred as the fourth fastest by any wicketkeeper. As per my records, it is the seventh fastest. Here it is:
Balls Keeper (Score) Countries Venue Season
81 Kamran Akmal (102*) Pak v Ind Lahore 2005-06
84 AC Gilchrist (122) Aus v Ind Mumbai 2000-01
84 AC Gilchrist (113*) Aus v Zim Perth 2003-04
86 AC Gilchrist (162) Aus v NZ W'ton 2004-05
88 JR Murray (101*) WI v NZ W'ton 1994-95
91 AC Gilchrist (138*) Aus v SA Cape Town 2001-02
93 MS Dhoni (116*) Ind v Pak Faisalabad 2005-06