i was making a list of cars/bikes i've owned and different engine configurations they were and apart from some highly exotic/unusual configs V5/W12/V10 i think i've ticked most of the boxes.
single
twin....parallel, V, boxer
triple....il, V3
4......il, V, boxer, square
forgot my merc 5 ...........il
6......il, V,box........llox
8.....V......
12....V
rotary.......2 & 3 rotor
c'mon and tell me what i've missed