That's a fantastic and very practical question for anyone managing public spaces. From my experience in urban design, there isn't one single "magic" material, but rather a combination that creates the most resilient solution. The top contender is often 304 or 316 grade stainless steel. It's incredibly tough, difficult to scratch or dent with common tools, and its non-porous surface makes it very resistant to spray paint and markers. Graffiti can usually be wiped off with a specialized cleaner without leaving a stain.
However, the material itself is just the start. The real game-changer is a high-quality powder coating or a proprietary polymer coating (like those used on public transit). These coatings add an extra layer of hardness and often incorporate a smooth, "sacrificial" layer that makes graffiti removal incredibly easy. Think of it as a non-stick pan for paint.
Design is equally crucial. A seamless, rounded design with minimal edges, grooves, or bolts eliminates spots where tools can get leverage to pry or peel. Anchoring the bin securely into concrete with tamper-proof fasteners is non-negotiable to prevent tipping or theft.
While concrete and heavy-duty plastics have their place, stainless steel with a professional-grade coating currently offers the best balance of resistance, maintenance, and longevity for high-vandalism areas. It's an investment, but it drastically reduces long-term repair and cleaning costs. The goal is to make the act of vandalism as difficult and unrewarding as possible.