Although I think most has been said on good deaths, I'll give my two cents (I feel like I should say I have researched a lot on 20th century wars so... my suggestions may be better suited for action/drama stories?) :
Types of deaths not mentioned/not commonly done:
-internal organs ruptures from nearby explosion reverberations- I don't think I've ever seen this happen in an action movie but it has happened in the past- the person doesn't look much different from the outside, which I guess would confuse the audience if done in a visual medium, but still.
- infections from open wounds or things like needles
- I know others have said illnesses and sicknesses, but idk if its just me, but usually I see too many 'died of unnamed fever just so the protag is more alone' (looking at you, disney parents), and tbh some illnesses are pretty horrible....
Personally I find 'villain falls of cliff/building so the hero doesn't have to actively kill someone' a pretty bad cliche, or the whole 'bad guys die from one bullet, but thirty bullets in him and the protag is still going strong' thing.
Also, as quite a few people have said, sudden, insignificant deaths can be really emotional to do (especially as it can feel more realistic and less fair, also less honourable), but then so can the traditional 'hold someone in your arms as they lie dying' stuff.
It does end up with what you want the characters death to do and what sort of genre you're writing for