What's your most surprisingly useful cycling gear/accessory under $30?

Okay, so we all know the big-ticket items: helmets, lights, decent pedals, good tyres. But I want to hear about the little things that ended up being total game changers. My pick: a small saddle bag with tyre levers and a patch kit. Saved me twice already on long solo rides. Other gems I’ve seen riders swear by:

• Phone mount that doesn't wobble
• Reflective ankle straps
• Gel seat cover
• Compact foldable rain poncho
• Bell with car-horn volume

What’s your pick for <$30 that makes every ride better?