If your cat goes outside at all, deworming is important. I personally love Revolution Plus, especially for my feral cats outside (I always try to tame them, so eventually they usually let me treat them monthly with a topical). There are a lot of good alternatives if your cat has a reaction to Revolution; for topical deworming, there's Profender or Advantage Multi; for oral deworming, Pyrantel pamoate is dirt cheap and effective--but has to be given once every 2 weeks until exposure or infection has resolved. This being said, the only cat in my house who gets treated with Revolution Plus is Cinnamon, who I take outside on a leash and harness during nice weather. The other 5 only get treated if there's an issue.
For vaccines, I will chime in and say FVRCP vaccine is really important for any cats that are ever exposed to cats living outside your home or if you volunteer at a rescue/shelter or do any kind of cat fostering. Panleukopenia is an awful, awful disease that can be fatal and extremely contagious; and FVRCP is extremely effective at preventing it. FVRCP also helps protect against common viral cold-like infections in cats, such as herpes. Of my 6 cats, all of them get FVRCP every 3 years except for Emily, who has autoimmune issues and the vet said she shouldn't get it. Having the other 5 stay current helps reduce her chance of infection too. And with a group larger than 4, there's always a chance of infections going around--even if they're not exposed to any cats outside the home.
My experience overseeing feline medical at a cat rescue--including several diabetics at the facility--taught me that preventing infections is usually much, much easier than treating an outbreak.