--V. Stokes
Does this count:
Clear[y];
{sol} = DSolve[{y'[t] == I*y[t], y[0] == 1},
y[t], t];
y[t_] = y[t] /. sol;
y[t] // InputForm
E^(I*t)
We could visualize it like so:
Graphics3D[Line[Table[{t, Re[y[t]], Im[y[t]]},
{t, 0, 20, 0.1}]]]
Mark McClure