Below are just a few of my favorite sleeveless designs in case you, too, are looking for a quick cast on!
Camisole no. 3

Bascom
I designed Bascom exactly with the idea of a classic, simple knit in mind. A rarity for me, the body is knit in the round so no mattress stitch is involved! Knit in Germantown Bulky in a classic textured ribbing, I'd make mine in honey.
Herbarium Slipover

Blomstring Slipover

Much more feminine than I usually go for, I really love the embroidery on this vest by Lærke from Fiber Tales. Another one that would look great in Lucky, I could also see it in a more modern styling with a bright color of Germantown like salmon.
Kelso

An elevated basic, Kelso is a lovely, simple tank designed by Meghan Kelly and knit in Mojave. I'd make mine in smoke gray, but am also considering one in Germantown to have a lovely little layering piece through the fall and winter!
High Tide Shell

I am very into this whole vibe, and especially the use of simple colorwork in this vest by Lindsey Fowler. Another one that would look great in Germantown.
Bruntsfield

Okay maybe an all-over stranded colorwork fingering weight vest is not, by definition, a "quickie", but Bruntsfield by Ysolda is just so lovely AND has steeking, which is incredibly satisfying. And a vest is still less knitting than a full sweater! I'd make mine in Camper.
Rosenlund
Another summer top, Rosenlund by Sari Nordlund. I'm imaging it in Scout for winter. All of the textured stitches would look great in autumn heather.
Ezra Vest

The Ezra Vest by Orlane Sucche feels like it would fit really seamlessly into my wardrobe. I like how there is a bit of visual interest and lovely detail (like the deep v neck and texture pattern) but is still simple and classic. I'd make mine in Cricket in moss.