C# - 325 319 chars
using System;class P{static void Main(){var s=Console.ReadLine().Split(' ');
var d=s[0].Split('-');int l=s[1][0]-48,x,y,r,a=int.Parse(d[0]),b=int.Parse(d[1]);
for(y=l;y>=-l;y--)for(x=-l;x<=l;)Console.Write((x==0&&y==0?'o':a<=(r=((int)
(Math.Atan2(y,x)*57.3)+360)%360)&&r
Newlines not significant.
Sample input/output
45-180 8
\||||||||////////
\\|||||||///////
\\\||||||//////
\\\\|||||/////
\\\\\||||////
\\\\\\|||///
\\\\\\\||//
\\\\\\\\|/
--------o
135-360 5
\
\\
\\\
\\\\
\\\\\
-----o-----
----/|\\\\\
---//||\\\\
--///|||\\\
-////||||\\
/////|||||\