To be frank, human beings have found ways to use just about every pokémon in war—even togekiss and blissey, pokémon who would be vehemently opposed to the concept. It’s a rather ugly subject, and I for one am staunchly opposed to the use of pokémon in active war zones myself. It’s one thing to engage in friendly battles with other trainers or to use pokémon in self-defense. It’s another thing entirely to put a pokémon’s life in danger for the sake of politics.
I think that among the few pokémon I’d be willing to talk about regarding the matter would be the medics, which consist of exactly the sorts of pokémon you would think: chansey, audino, wigglytuff, and all others used by Nurse Joys. Blissey tend to be the most prevalent for this purpose, as their healing abilities are the most potent of all. Medic pokémon are also sometimes used for more domestic purposes on military bases, such as cooking, unloading supplies—even helping to train new recruits (although the latter function is usually handled by fighting- and rock-types).
Then, of course, there are “sniffer pokémon,” or pokémon trained specifically to hunt for mines. These are used during peacetime in certain countries as well, as those nations frequently have active minefields from past wars. Quite a few pokémon may fit this description, but rattata’s light weight, combined with its keen sense of smell, have made it a prevalent sniffer pokémon as of late.
Finally, of course, there are togekiss, which are less used and more seen guiding civilians to safety and protecting them from the less pleasant aspects of living in a war zone. Some ghost-types, such as members of the yamask line, have also been known to do this.
Then, of course, you have the plethora of pokémon who are used as soldiers, as mentioned above, but … I would rather refrain from describing all the ways any given military force has used pokémon for active warfare. I know that it would be far more professional to prevent my feelings on the matter from getting in the way of my ability to answer a valid question, but it’s not just because the actual details are rather horrific, anonymous. It’s because human beings are extremely creative when it comes to finding ways to turn things into weapons. Think of anything a human being would do during a war. Literally anything. Humans have figured out how to use pokémon to do it, and that’s only part of the list of what uses humans have found for pokémon during a war. If you recall news from a decade or two ago, you may remember that some of the things we’ve used pokémon for are technically war crimes.
That should give you an idea of how wide the spectrum is. On one end, you have medical pokémon, training pokémon, and perhaps a few normal-types assisting with administrative work. On the other, you have … well. You probably remember.
So it’s likely understandable that I’m a bit uncomfortable with the subject.
The Pokédex According to Bill 