Bulk Material Creator for Unity3d. Just select your textures, then select from the menu Assets > Bulk Material Creator, assign a shader and hit create. MIT License.

gistfile1.cs

using UnityEngine;
using UnityEditor;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

public class BulkMaterialCreator : ScriptableWizard
{
  public Shader Shader;

  [MenuItem("Assets/Bulk Material Creator")]
  static void CreateWizard() {
    ScriptableWizard.DisplayWizard("Bulk Material Creator",typeof(BulkMaterialCreator));
  }

  void OnWizardUpdate() {
  }

  void OnWizardCreate() {
    foreach (var obj in Selection.objects) {
      if (obj.GetType() == typeof(Texture2D)) {
        var texture = (Texture2D)obj;
        var material = GenerateMaterial(texture);
        var path = GetDirectory(obj) + "/" + material.name + ".mat";
        AssetDatabase.CreateAsset(material, path);
      }
    }
  }

  private Material GenerateMaterial(Texture2D texture) {
    var material = new Material(Shader);
    material.name = texture.name;
    material.mainTexture = texture;
    return material;
  }

  private string GetDirectory(Object obj) {
    var path = AssetDatabase.GetAssetPath(obj);
    if (path.Contains('/')) {
      path = path.Substring(0, path.LastIndexOf('/'));
    }
    return path;
  }
}

I modified this script to allow changing which property to apply the texture to and add a suffix to the material name

using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UnityEditor;
using UnityEngine;

public class BulkMaterialCreator : ScriptableWizard {

	public string PropertyName = "_MainTex";
	public string Suffix;
	public Shader Shader;

	[MenuItem(itemName: "Assets/Bulk Material Creator")]
	public static void CreateWizard() => DisplayWizard(title: "Bulk Material Creator", klass: typeof(BulkMaterialCreator));

	public void OnWizardUpdate() { }

	public void OnWizardCreate() {
		foreach (var obj in Selection.objects) {
			if (obj.GetType() == typeof(Texture2D)) {
				Texture2D texture = (Texture2D)obj;
				Material material = GenerateMaterial(texture);
				string path = GetDirectory(obj) + "/" + material.name + ".mat";
				AssetDatabase.CreateAsset(asset: material, path);
			}
		}
	}

	private Material GenerateMaterial(Texture2D texture) {
		Material material = new Material(shader: Shader);
		material.name = texture.name + Suffix;
		material.SetTexture(name: PropertyName, value: texture);
		return material;
	}

	private string GetDirectory(Object obj) {
		string path = AssetDatabase.GetAssetPath(assetObject: obj);
		if (path.Contains(value: '/')) {
			path = path.Substring(startIndex: 0, length: path.LastIndexOf(value: '/'));
		}
		return path;
	}
}

Useful for VRChat MatCap Lit shader using property _MatCap