What is in your gym bag?

I live close to the gym, so I just wear my outfit there and shower at home. Bag usually just has my massive, ridiculous, stability shoes, which pretty much fill it; lock; water; earphones.

Sometimes I bring a bar of soap and a very thin towel if I plan on doing something immediately after the gym.

For swimming days, swim cap, suit, goggles, towel, sandals for shower, vaseline for face (have mild rosacea, chlorine aggravates it), soap, travel-sized bottle of shampoo. Plastic shopping bags (for the wet sandals and suit). I do a real shower at home.

When I went to a gym closer to where I worked, which had amazing showers and free towels, I kept a full stock of toiletries, plus shoes, in a rented locker. Day to day, I just brought gym clothes and clean undies and socks to wear home or out. If I went out afterwards, I left things to be washed there, to get the next day. This was super convenient.

On days when I go to the gym from home I just take a string bag with my phone, mp3 and headphones, hand towel, water and something to read on the treadmill.

If I am going on my way home I use a duffel bag. I got a great deal on a Nike bag at Target. In that bag I keep the following.
Workout clothes
Hand towel
Swim suit and towel
Deodorant
Hair ties and clips
Toothbrush and toothpaste (just in case)
Ace bandage
Tennis ball (to stretch my feet)
Arm band for cell phone
Comb
Lock

I try to keep things in there that I may need if out am not going home first.