In the category .NET trivia. I found a weird difference between .NET 2.0 x86 and x64. This code detects that it runs on x64 (at least the .NET 2.0 build included with Vista x64):

WeakReference r = new WeakReference(null);
try { throw new Exception(); }
catch (Exception x) { r.Target = x; }
GC.Collect();
if (r.Target != null)
  Console.WriteLine("Running on x64");

It appears that the last thrown exception is stored in a global (or rather probably thread local) variable and hence not garbage collectable until the next exception is thrown...

Update: I thought this was obvious, but since two commenters have felt the need to point out that you shouldn't use this in production, I'll say it explicitly:I was just pointing out some obscure implementation difference (arguably a bug), do not use this code in production.