I use nothing but Delta 400. I've been using a homemade high-sulfite ascorbic acid developer similar to Xtol, but lately I've had my eyes opened to MC-TEA. It produces very fine grain for a non-solvent developer and fantastic accutance. If you plan on making large enlargements, this is the way to go. The downside: you need to expose at 160. I don't think there's a commercial developer that replicates the look.
There's a post in the recipes section, but I'll make it more legible here:
100ml triethanolamine
35g ascorbic acid/dehydroascorbic acid mixture sold as C-1000 by the Vitamin Shoppe. It's the equivalent of about 25g pure ascorbic acid.
6g metol
Heat the mixture till the metol and ascorbic acid dissolve. Then add TEA to 150 ml (otherwise the chemicals will come out of solution when the TEA cools).
Use at 1:100, with the addition of 10 g of sodium sulfite (2tsp) per liter of working solution. 12 mins at 74F for Delta 400 35mm.