Whatever is on my feet at the time. I used to have a pair of Solomon Aquamphibians. Best shoes ever, but the puppy liked them more than me.  Here lately it's been my house slippers, because they're so warm and comfy.

If its even close to warm its flip flops, till i get in to the boat and then they come off immediatly then usually my shirt.... not pretty but comfortable... ask nuclearpenguin he has seen this sight

You girls must not fish when it's cold!

nope.  ;D

North Face, light weight, comfortable and air-drys pretty well.

If I'm shore fishing when it's cold, I just wear my hunting boots. On the boat, I wear my Sperry top-siders or Sperry Figawi's.

Falcon

If its really cold weather I've got a pair of Merrell hiking boots I wear. Summer if I'm not getting my feet wet I wear a pair of New Balance tennis shoes. For this summer I'm going to pick up a pair of sandals or water shoes similar to these Keen's.

http://www.basspro.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10151&catalogId=10001&langId=-1&partNumber=72990&hvarTarget=search&cmCat=SearchResults

Whichever shoes I put on that day-more often than not, sneakers

< 50 degrees - Goretex thinsulate hiking boots with smartwool socks

> 50 up to 70 - tennis shoes

70> Columbia sandals

I also have a pair of North Face lightweight boat shoes that I like.

Flip flops when it is worm, Good ole' Steel toes when it is cold.

Crocs when it is warm and New Balance tennis shoes any other time.  I have to admit though that the tennis shoes are a superstition and I carry them in the boat even when I wear the crocs.  I have been known to put them on when the bite is tough.  

Asics Gel Kayanos. The cushiness of the gel pads in the forefoot and heel is great, IMO:o)

NB Tennis shoes for support for long days on the water.  In colder temps I wear heavy wool socks with a poly pro liner sock under them.  They keep you feet warm and I figure if I'd fall in I can swim in them better than a pair of heavy boots.

I tried the barefoot thing in the heat of summer once.  Only problem is I'm a guy that always has at least a half dozen rods on the deck.  It only takes one #2 treble in your big toe to make you keep your shoes on.  No matter how hot it gets.