On September 10, 2018 (2017 in most of the world), elections were held in Maine for the 39 members of the Exalted Chamber of the Councillors Under God. Elections were held under a system where each county got one councilor for each city within its borders plus one, which has fallen under criticism for not fairly representing the people. This issue was clearly shown in this election, as while the English List won the popular vote by over 12% (or 6%, if the areas of questionable electoral integrity in Cumberland are to be removed), the Liste François had a majority of one seat in the Chamber (which, if the areas of questionable electoral integrity in Cumberland were removed, would have been a majority of three).
In a bit of a different direction from the above... here's a hypothetical US Senate reformed with the idea of 'degressive proportionality'-essentially the idea that "the subdivisions do not each elect an equal number of members, but smaller subdivisions are allocated more seats than would be allocated strictly in proportion to their population", with the German upper legislature being an example of this
Here, the 'electoral vote' numbers are the number of senators each state gets. Each state will have at least 2. If a state has at least 1 million people, it will have 3 senators, and from there, each additional senator is gained when the population doubles (so, a fourth senator for states with at least 2 million people, a fifth with at least 4 million people, a tenth with at least 128 million people, and so on), with the numbers adjusted along with the House reapportionment after the census every 10 years
In real life, this reform would likely never be enacted because it would (1) largely just benefit one party and (2) would possibly not just require an amendment but rather some sort of super-amendment with all 50 states agreeing to it, due to a clause in the constitution that says the clause requiring all states to have equal representation in the senate (though that clause could arguably just be removed by a regular amendment, allowing the clause requiring all states to have equal representation in the senate to then be modified or removed via simple amendment rather than one adopted by all 50 states)
That being said, there are those who argue that we should just have one-person-one-vote, and one might say that the US has developed more in the direction of direct vs indirect elections and has less need today for equal representation to each state. This here hypothetical Senate reform could perhaps be seen as a more 'modern' take on the Connecticut Compromise between equal and proportional representation, shifted more towards proportionality but not fully removing smaller states' greater weight per person (with the four largest states having ~33% the US population but just 13% of senators, and the 26 smallest states having just ~18% of the population while having 37% of senators)