"Essential" tarot spreads

I am looking to expand my knowledge of and comfort with different tarot spreads. Up to this point I have generally used three card spreads (no positions or positions determined by the issue or question at hand) and the Celtic Cross. I'd like to branch out and be more flexible. What do you consider the top one or two tarot spreads that every reader should know?

For me:
1) Celtic Cross
2) An eight-card horseshoe spread (which I call "How You Doin'?") with positions that go: Body/Mind/Spirit/Friends/Family/Relationships/Career/Finances. Positions can be added if needed, such as for Pets, and by throwing two cards in each position, a "Present/Future" spread can be created, or "Current Situation/Advice" or what have you. It is very versatile.
3) Three card "Do/Don't Do/Advice" spread. I have found this one especially helpful for situations when the querent wants to help another person, isn't sure what to do, and doesn't want to get too deep into the details of what is happening with that person, or to intrude on private matters.
4) Ten Card "If and When" spread. This is for questions such as, "Will I ever get married?" Lay out ten cards. If a card representing the desired outcome shows up (such as 4 of Wands, The Empress, etc. in my example), the answer is "Yes," and the closer to the beginning the desired card shows up, the nearer in time the outcome will occur. Cards leading up to the desired outcome card show events on the path to the outcome, or what is needed in order to bring forth the outcome. (If no card shows up depicting the desired outcome, then I might go on to a Celtic Cross to see what is blocking this from materializing in the querent's life.)

Five-Card 'Wheel Spread':

---1

4--5--2

---3

1) Present situation
2) Waning influences
3) Hidden or unconscious influences
4) Emerging influences
5) Synthesis: what will reconcile or unify the other four factors in the reading.

This is from 'Power Tarot' by MacGregor & Vega; has more than 100 different spreads. My classes used to enjoy this spread (fewer cards than a CC), but the 5th card is usually the most difficult to read.

Thank you for these recommendations. Apollonia, I particularly like your take on the Horseshoe spread; one of the reasons I want to expand my spread vocabulary is that as is I end up using the Celtic Cross for general readings, and while I've had success with it that way, it's really a "question" spread rather than a "general overview" one. Tarot bear, interesting how your spread is similar to the first half of the Celtic Cross. I can see how that last card would be challenging to read but I do want to try it out and see how it works in practice!