Stuff like “god damn”, “fucking hell”, etc. Anything that stems from religious sources. That includes fudged varieties like “jeez/geez” and “heck”.
And to clarify, this isn’t some attempt to avoid blasphemy or anything. I’m not particularly religious and would rather rewrite the neural pathways for those “defaults”, but haven’t been able to come up with satisfactory alternatives so far.
*To clarify further, I’m all good with most other curses (shit, fuck, ass, etc). I’m not trying to be inoffensive, just non-religious.
I use “fucking terts” when I’m angry at a specific person (“terts” is a derogatory term for earth humans (from Alien Nation), and “furless human” when I’m in a slightly amused mood (it’s what my cat used to curse me).