Rogue 12/Fighter 8 is a pretty tasty end goal, if only for the maximum ASI's (7), as well as nabbing/not losing out on (sub)class features. It does, however, depend on what your focus is and what subclasses you're playing. An Assassin, for example, might happily forgo their 13th level feature, while a Thief might really want UMD asap.

To answer more specifically;

- Arcane Trickster/Eldritch Knight is an obvious combo, for the spell slots; with this one, you'll probably want a heavier focus on one Class to get access to the higher level spells known and subclass features. A 15/5 split is not unreasonable here.

- Champion/Anything is nothing to shout about, but is also nothing to complain about either; Improved Crit + Sneak Attack is all kinds of tasty (and adding both Str and Dex mod to your jump distance is sort of entertaining too!).

- My personal favourite has to be Mastermind/Battlemaster, though. Yeah, there's a little overlap, but it makes for a great former (non-comm) officer style character, who knows war (and people) from extensive experience; good for middle-aged human or any of the longer lived races that want to play up on the "You're all kids to me" aspect of playing such a race.