Ideal Amplifier Spice Model

.subckt amplifier 1 2 3 4
B1 1 0 I=0
B2 2 0 V=(1/-I(B3))*V(1)
B3 3 4 V=1
R1 4 0 .0000001f
.ends

1 is input, 2 is output, and the amplifier's gain is the resistance between 3 and 4.