Compared to the other comments my answer is really bland!

Pesto

I just really really really like pasta al pesto. No versatility, no multiple uses. Just the one dish but man i love it

Here are my indispensable condiments and/or sauces:

• 腐乳 (fǔrǔ, or "fermented bean curd"). If you've been in a Chinese grocery and saw the red or yellow cubes in a suspicious-looking slightly translucent liquid, that's the stuff. I use it in congee. I use it on steamed buns like butter (spread very thin). I toss a cube into a stir-fry to give it an instant lightly-sour, heavy-umami boost. It works well to jazz up slightly under-developed noodle soups too if you screwed up the broth and found out too late.
• 豆豉酱 (dòu chǐ jiàng, or "fermented black bean sauce"). This is most popularly (for a good reason!) the 老干妈风味豆豉辣椒酱 (Lǎo Gānmā fēngwèi dòuchǐ làjiāo jiàng, or "Lao Ganma fermented black bean chili sauce). Lao Ganma (literally "old dry mother" but more accurately "old godmother") is a China-wide brand that has absolutely nailed this sauce. The only time I've had it better was made from scratch by a withered lady from Guizhou. The various sauce-alikes in grocery stores are inferior copies.
• 剁辣椒 (duò là jiāo, or "[Hunan] chopped peppers"). This is a Hunan export that uses chilies grown in Hunan's terroir that then ... well ... as the name suggests, get chopped. They're then salted/pickled. It sounds simple, because it is, but that simple process results in the weirdest ambrosia I've tasted in my life. You want to liven up purple taro? Throw in a spoon or ten of this and what was once a pleasant, but a bit drab, staple turns into a lively, tasty thing that people look forward to eating. It can also be used, like the furu above, to spice up a drab stir-fry like bok choi or other leafy greens. It is used as a marinade for roasted chickens. And when I make OTHER pickles (like pickled string beans) a spoonful of this mixed in gives it a really nice sparkle.

A good hot sauce (that has flavor and not just heat) for versatility and to save some bland foods. Also soy sauce; it’s essential to many of my favorite Asian recipes.

Mayo. Not for the mayo itself, but because to make any aioli you must start with mayo. And aioli is fucking amazing for so many things. If you ever had a next level meal at a restaurant it was probably because of an aioli.

I know it's supposed to be a dip, but I treat hummus like a condiment half the time.

Love it to the point I eat it straight.

I'm a huge sauce and condiment slut, so it's hard to narrow it down. Sweet chili is versatile. Fish sauce, soy sauce, and hoisin are indispensable. Horseradish sauce and tomato paste are also staples.

As far as brands go, though, Marie Sharp's hot sauces are my absolute favorites. I love Caribbean food, though, so I'm biased. Now I want to make wings.

Love

Ponzu

Sriracha. The ole 'rooster juice.'

Also sliced roasted green chiles. Almost anywhere you use a regular condiment, these work better.

Lemon hot sauce.

Red hot.

Gun powder. A chili powder mixture from Ethiopia which is really strong but also really tasty. Makes everything great

South African mayo.

Chicken salt

I used to like ketchup a lot and used it on a lot of things. Maybe I've aged out of it or maybe the ketchup has changed but I now call it red sugar sauce. It is way to sweet for my liking.