My personal choice is a chene or fluke type anchor. They bite very well in sand, mud or gravel and hold well, even in current or wind. I used a small chene anchor on my Sea Nymph 16' and it did great. I now have a 20' cuddy and use the same style anchor, although this one is bigger. It holds my boat in currents in the Ohio River of 3 mph or so. That takes some grip. I like them because they don't weigh a ton and are easy to retrieve. I see guys with the 15-20 lb mushrooms, Crab Claws and anchors like that and they are awful to pull up. Retrieve that anchor 5 or 6 times a day and see what your fingers look like- pretty sore.
The chene anchors don't bring up a ton of bottom goop either. Just make sure you use a section of chain to attach the anchor to the rope with so it digs in properly.
UFM82