By 'realistic' I mean ones which have a good chance of happening with someone.
Kant's ethics applies to all situations in which somebody does an intentional action. So looking for a range of 'realistic' - real life, true to life, matter of fact, everyday, &c. - situations to which it applies misses its totally general applicability. It is relevant right across the piece. No intentional action escapes its scope.
Time to bring things down to ground level. Suppose you want to borrow $100. Do you intend to pay it back ? If you don't, then your implicit policy - the 'maxim' of your action, as Kant would put it - is 'Whenever I want money I can borrow it without paying it back'. To simplify a bit, Kant tells us to test whether such a policy or maxim would be 'universalised' - become a policy or maxim on which everyone could act or in Kant's words whether it could be a 'universal law'.
It's plain to see that such a policy could not be universalised since no-one would or could lend, knowing that the borrower had no intention of paying back. The practice of borrowing would collapse. I might give you the money you want but I can't lend except on condition that I expect payment back; but under this universal law of conduct - of non-repayment - I cannot expect this since no-one will pay anyone back.
Universal laws are important to Kant - there is a requirement to universalise our policies or maxims - because Kant sees us as rational agents; and as rational we must act in a law-like way, in a way consistent with everybody else's acting in the very same way.
It's nothing against Kant that in fact most people some of the time, and some people most of the time, don't act in this universalisable manner - that their policies or maxims could not be 'universal laws'. He is not assessing our psychology; he is telling us what is required of us as rational agents.
It turns out, for reasons a little too involved to explain here, that in acting on universal laws we act morally as morality is ordinarily understood. The example of borrowing illustrates the point. Along the lines of ordinary moral thinking we have a moral obligation in normal circumstances to repay what we have borrowed; and as we saw in 3. above, Kant's requirement of universalisability rules out flouting this obligation.
A condensed expression of Kant’s ethics is the categorical imperative:
Act only according to that maxim whereby you can, at the same time, will that it should become a universal law.
The epithet „universal“ indicates that one should remove from a candidate maxim all references to a particular group of people. A feasible maxim is free from discriminating any particular group of persons.
This property is characteristic for today’s human rights.
Hence Kantian ethics applies to check any candidate for a future human right.