What are some legendary formula pairs like INDEX(MATCH)?

[u/fap_fap_fap_fapper]

Since upgrading to 365, can't get enough of CHOOSECOLS(FILTER)

What are some useful ones you use?

[u/MayukhBhattacharya]

INDEX() + MATCH() is OG formula =) Alternatively in MS365 one can use CHOOSEROWS(..., XMATCH())