V16 Engines
Inline 3, 4, 5, and 6
V6, V8, V10 and V12
Boxer 4 and 6
W8, W12, W16, W18
Wankel Rotaries
Flat 4, Flat 6, Flat 8
Inline 8
V4
Two Strokes
Diesels
Hybrids
Electric
But we forgot one more!
The V16 which is originally developed by GM of their Cadillac Division in the 1930's and it's the biggest production engine of history!(Literally!)

And they used through 1930-1940!And It's sort of shaped like a U.
And in 2002 or 2003 they used this engine in their concept car called the sixteen.

V16 Engine

Concept car
And now the current production one is Bugatti which is the W16!