I like the election of 1874 for being an election that followed a change of government, rather one that produced a change of government. In the fall of 1873 the House of Commons, barely one year into its five year life following the 1872 election, decided it no longer supported the government of John A. Macdonald. (There was a little contretemps called the Pacific Scandal.) Macdonald's government resigned, and the Governor General invited Alexander Mackenzie, to whose Liberal Party many of Macdonald's former supporters in the House had transferred their support, to form a new government.
He did, and he initially expected to govern for some time.Parliamentary government was taken seriously in those times; no one doubted the authority of the people's elected representatives to make and unmake governments between elections. But results in a by-election looked so promising for the Liberals' prospects that the new government soon pulled the plug. Worked too: in a post-election House that had grown to 206 members, Mackenzie had the support of about 133.
Mackenzie called the election before bringing in the electoral reform plans the Liberals had promised for some time. So this was the last general election before the secret ballot. It was, however, the first in which practically all constituencies voted on the same day.
[Source notes: I'm relying quite a bit on the Parliamentary website record of federal elections, on Wikipedia's similar list (a bit dodgy in places, I think), and John Duffy's terrific electoral history Fights of our Lives, plus the DCB and various specific period histories. Errors and corrections gratefully received. Interpretations and emphases my own.]