This is related to this question: How to give some boost to some really good answers that arrive late?, but I thought it warranted its own feature-request.
Something I've thought might be a good idea would be to give each user a small number of Supervotes per day. These would be worth several normal votes, would possibly cost some rep, and would be rationed to maybe 3 per day (as opposed to the 30(?) per day limit for normal votes).
Sometimes you see answers that are so good you want to upvote them really hard. This would be a way to do it.
(But it complicates the voting system and the UI, and probably isn't worth the costs. Discuss. 8-)