Utility class that re-throws a throwable as unchecked?

Yes, there is a way to write a method that will avoid wrapping your checked exceptions. For this use case it is a perfect match, although you should definitely be very careful with it, since it can easily confuse the uninitiated. Here it is:

@SuppressWarnings("unchecked")
public static <T extends Throwable> void sneakyThrow(Throwable t) throws T {
    throw (T) t;
}

and you'd use it as

catch (Throwable t) { sneakyThrow(t); }

As commented by Joachim Sauer, in certain cases it helps convince the compiler that the line calling sneakyThrow causes the method to terminate. We can just change the declared return type:

@SuppressWarnings("unchecked")
public static <T extends Throwable> T sneakyThrow(Throwable t) throws T {
    throw (T) t;
}

and use it like this:

catch (Throwable t) { throw sneakyThrow(t); }

For educational purposes it is nice to see what's going on at the bytecode level. The relevant snippet from javap -verbose UncheckedThrower:

public static <T extends java.lang.Throwable> java.lang.RuntimeException sneakyThrow(java.lang.Throwable) throws T;
  descriptor: (Ljava/lang/Throwable;)Ljava/lang/RuntimeException;
  flags: ACC_PUBLIC, ACC_STATIC
  Code:
    stack=1, locals=1, args_size=1
       0: aload_0
       1: athrow
  Exceptions:
    throws java.lang.Throwable
  Signature: #13                          // <T:Ljava/lang/Throwable;>(Ljava/lang/Throwable;)Ljava/lang/RuntimeException;^TT;

Note there is no checkcast instruction. The method even legitimately declares to throw T, which can be any Throwable.

The great Guava library has a Method Throwables.propagate(Throwable) that does exactly what your code is doing: JavaDoc

From the doc:

Propagates throwable as-is if it is an instance of RuntimeException or Error, or else as a last resort, wraps it in a RuntimeException then propagates.