The minimalist teleological argument I like to defend goes like this:
1. Whatever exhibits regularity is not the result of chance alone. (Premise)
2. The laws of nature exhibit regularity. (Premise)
3. Therefore, the laws of nature are not the result of chance alone. (From 1 and 2)
This is such a straightforward argument and its strength lies in its highly intuitively true premises. The observation that there are laws of nature is proof enough that they are the result of someone's or something's providence. Theists and pantheists alike call this someone or something, "God." Of course, as a theist, I hold that the laws of nature are the result of someone's providence, e.g. design.
Let's ask ourselves: is this belief at least rationally acceptable? In other words, is it positively irrational to believe that the laws of nature are the result of design? It's difficult to see how such a belief could be irrational. First, take the proposition, "it is necessarily the case that the laws of nature are not the result of design." Is there any forthcoming argument in support of this? If there's not, then it's at least possible for the laws of nature to have been designed. If this is so, then we have a potential cosmo-teleological argument for God's existence.
4. Possibly, everything that exists has an explanation of its existence, either in the necessity of its own nature or in an external cause. (Premise; W-PSR)
5. If the laws of nature are designed, that designer must be timeless, changeless, immaterial, very powerful and very intelligent. (Premise)
6. Possibly, the laws of nature are designed. (Premise)
7. Possibly, a timeless, changeless, immaterial, very powerful and very intelligent designer exists. (From 5 and 6)
8. Necessarily, a possible designer will either exist by a necessity of its own nature or in an external cause. (Implied by 4)
9. Necessarily, a timeless and changeless designer cannot have an external cause. (Premise)
10. Therefore, a designer exists by a necessity of its own nature. (From 4, 7 and 9)
To be honest, I think this is a rationally compelling argument. However, I'm willing to grant for the sake of argument that not each of the argument's premises is rationally compelling. Hence, I'm arguing instead for the rational acceptability of the argument. That is indeed one of the primary objectives of natural theology, and I think the argument is successful in showing that theism proper is, at the bare minimal, rationally acceptable.