what do you think is the greatest sign of friendship

[Evil Yoshi Toes]

To me a great sign of friendship is someone going out of their comfort zone to make you happy. For example, a hug from a friend who is typically aloof with people, or a friend who hates the outdoors going on a hike with you. They're subtle kind acts that from some people may not mean a lot, but when they come from a certain friend who you don't expect it from it's very heartwarming.

If you want to be really dramatic then taking a bullet (in the literal sense) for your friend is pretty nice, but most of us won't find ourselves in that situation thankfully.