My first suggestion would be a FourSevens Preon 2 (P2).
Despite the fact I'm less of a fan of their AA and 123 lights than I've been in the past, the HCRI Preon 2 I have continues to impress me. They're getting hard to find now though, but I think GoingGear may still have a few.
The clicky tailcap the P2 comes with can be a little finicky, but you can easily swap it out with a fixed tailcap that will turn it into a twisty, and you can also get a 1xAAA body if you like as well. The output levels are excellent (I think they're something like 3, 30, and 150 lumens), so they're well spaced, and the high output is great enough that I don't feel like I need to carry another light with me that runs on AAs or some other type of larger cell to give more power when I want it. So, it also works for me as a full-fledged EDC light. The only disadvantage is that AAAs have a lot less run time than AAs.
My second suggestion would be an EagleTac D25A2. They're available as either a twisty or a clicky, and are much better built than the FourSevens Mini AA2 is. The biggest disadvantage is that you can't easily change back and forth between twisty and clicky like with the Preons; you need to buy an entire new body to do that, so you end up just switching the head between the two bodies. Another advantage, other than the stout build quality, is that they're AA based lights, and aren't really much bigger than AAA lights, so you'll get a LOT more run time out of them. So if you need run-time and durability, get an EagleTac; if you need the smallest size and lightest weight possible, and need something that looks nice enough to carry at work, business meetings, etc., the Preon 2 is the way to go.
These are the two best lights in the small penlight category IMHO, and I don't think you'd really go wrong with either.