Offline games like Skyrim can be interesting with some of the command console cheats like spawning multiple dragons in a city or whatnot. Some of the trainers can add in some interesting gameplay as well.
If your talking about online games then I would advise against it as it's almost a guaranteed ban (rightfully so). Pretty much any game that has a online element I would advise against using trainers even if it's only a leaderboard chart as some ridiculously high score that would be impossible otherwise is bound to attract some attention and may lead to a ban.
EDIT: Using one on RDR2 (even if offline only) could be risky and may result in ban, I wouldn't recommend using one.