Glock 17s, and Glock 19s are both good choices. Depending on where you order from, most places have the "full metal" version of the glock, which has a metal slide and barrel, instead of plastic. The Glock 34s are also nice, minus the fact that none of them include a metal slide.
As mentioned earlier, the Glock 18C is going to break, and eventually only work in full auto. If you want a Glock26C, I haven't heard anything about those breaking and only firing in full auto.
Just about everything is a good choice, so no matter what you choose, you won't be disappointed.