Monk
Monk is the sort of character who's components can be traced, and this amalgam could make him seem like a compilation of other detectives. But he is an original character. This is the process Evelyn Waugh used, albeit compounding people he knew.
Like Sherlock Holmes, Monk is incapable of not being inquisitive. He notices incredibly small things and plays Holmes' trick of surprising people by telling them deeply personal information about themselves within minutes (or sometimes seconds) of meeting them. He also shares Holmes' vast knowledge of ephemera — he knows the details of different models of rifle, and can identify cigarette brands by smelling a curtain.
He has Poirot's obsessive neatness: in one episode he sees two coffees pots, one with more in than the other, and evens out the amount of coffee in them, not caring that he has mixed caff and de-caff. This comes with Poirot's resistance to accepting disorderly solutions, which is often the way he cracks the case.
From Columbo, he inherits a sense of unworldliness, distraction and sometimes a disarming ability to challenge a suspect. They both also irritate people on first meeting, partly because they are odd, partly because they don't accept the verdict — but when they find the solution people are amazed by them.
All of the episodes are available on Amazon Prime and it is one of the best television detective programmes, obviously coming in behind Columbo and Murder She Wrote, but perhaps not always and not by very far. The best episodes are truly excellent.
The format changes between who dunnit and how dunnit, and the locations are varied as well: aeroplanes, schools, earthquakes. Some of them can be worked out, but the solutions are often impressive.
Do watch it.