Add text into your Unity Game/Scene view using only a script. Basically Debug.Log for runtime text.

DebugText.cs

// Source : https://gist.github.com/kkukshtel/3cec9473bb5eda90635f1765e259498d
// Modifications identified by comment starting with HACK tag

using UnityEngine;


namespace OddTales.Framework.Core.Other
{
    public static class DebugText
    {
        static float defaultXScale = .1f;
        static float defaultYScale = .1f;
        static float defaultKerning = .25f;

        // Write along the x axis, facing positive z
        public static void Write(string text, Vector3 position) { Write(text, position, Vector3.right, Vector3.forward, Color.yellow, defaultXScale, defaultYScale, defaultKerning); }
        public static void Write(string text, Vector3 position, Color c) { Write(text, position, Vector3.right, Vector3.forward, c, defaultXScale, defaultYScale, defaultKerning); }
        public static void Write(string text, Vector3 position, Vector3 writeDirection, Vector3 lookDirection) { Write(text, position, writeDirection, lookDirection, Color.yellow, defaultXScale, defaultYScale, defaultKerning); }
        public static void Write(string text, Vector3 position, Vector3 writeDirection, Vector3 lookDirection, Color color) { Write(text, position, writeDirection, lookDirection, color, defaultXScale, defaultYScale, defaultKerning); }
        public static void Write(string text, Vector3 position, Vector3 writeDirection, Vector3 lookDirection, Color color, float xScale, float yScale) { Write(text, position, writeDirection, lookDirection, color, xScale, yScale, defaultKerning); }


        public static void Write(string text, Vector3 position, Vector3 writeDirection, Vector3 lookDirection, Color color, float xScale, float yScale, float kerning)
        {
            Vector3 normWrite = Vector3.Normalize(writeDirection);
            Vector3 normLook = Vector3.Normalize(lookDirection);
            Quaternion q = Quaternion.LookRotation(normLook, Vector3.Cross(normLook, normWrite));
            char[] charText = text.ToUpper().ToCharArray();
            float offset = 0;
            for (int i = 0; i < text.Length; i++)
            {
                int[] instruction = DebugLetters.GetCharInstructions(charText[i]);
                for (int l = 0; l < instruction.Length; l++)
                {
                    if (l + 3 >= instruction.Length) { break; }
                    Matrix4x4 m = Matrix4x4.TRS(Vector3.zero, q, Vector3.one);
                    Vector3 start = new Vector3(position.x + ((offset + instruction[l]) * xScale), position.y + (instruction[l + 1] * yScale), position.z); // HACK : position no longer affected by scale
                    Vector3 end = new Vector3(position.x + ((offset + instruction[l + 2]) * xScale), position.y + (instruction[l + 3] * yScale), position.z); // HACK : position no longer affected by scale
                    start = m.MultiplyPoint3x4(start);
                    end = m.MultiplyPoint3x4(end);
                    Debug.DrawLine(start, end, color);
                    l++;
                }
                offset += (2 + kerning); // 2 is width of a single letter
            }
        }
    }


    // HACK : replaced public by internal so DebugLetters can only be used by DebugText class
    internal static class DebugLetters
    {
        public static int[] GetCharInstructions(char c)
        {
            switch (c)
            {
                case 'A': return A;
                case 'B': return B;
                case 'C': return C;
                case 'D': return D;
                case 'E': return E;
                case 'F': return F;
                case 'G': return G;
                case 'H': return H;
                case 'I': return I;
                case 'J': return J;
                case 'K': return K;
                case 'L': return L;
                case 'M': return M;
                case 'N': return N;
                case 'O': return O;
                case 'P': return P;
                case 'Q': return Q;
                case 'R': return R;
                case 'S': return S;
                case 'T': return T;
                case 'U': return U;
                case 'V': return V;
                case 'W': return W;
                case 'X': return X;
                case 'Y': return Y;
                case 'Z': return Z;
                case '0': return zero;
                case '1': return one;
                case '2': return two;
                case '3': return three;
                case '4': return four;
                case '5': return five;
                case '6': return six;
                case '7': return seven;
                case '8': return eight;
                case '9': return nine;
                default: return new int[0];
            }
        }

        /*
            0,2   1,2   2,2
            0,1   1,1   2,1
            0,0   1,0   2,0
         */
        public static int[] A = new int[]
        {
            0, 0,
            0, 2,
            2, 2,
            2, 0,
            2, 1,
            0, 1,
        };

        public static int[] B = new int[] { 0, 0, 2, 0, 2, 2, 0, 2, 1, 2, 1, 0, 1, 1, 2, 1 };
        public static int[] C = new int[] { 2, 2, 0, 2, 0, 0, 2, 0 };
        public static int[] D = new int[] { 0, 2, 2, 2, 2, 0, 0, 0, 1, 0, 1, 2 };
        public static int[] E = new int[] { 2, 2, 0, 2, 0, 0, 2, 0, 0, 0, 0, 1, 1, 1 };
        public static int[] F = new int[] { 0, 0, 0, 2, 2, 2, 0, 2, 0, 1, 2, 1 };
        public static int[] G = new int[] { 2, 2, 0, 2, 0, 0, 2, 0, 2, 1, 1, 1 };
        public static int[] H = new int[] { 0, 0, 0, 2, 0, 1, 2, 1, 2, 2, 2, 0 };
        public static int[] I = new int[] { 0, 0, 2, 0, 1, 0, 1, 2, 0, 2, 2, 2 };
        public static int[] J = new int[] { 1, 2, 2, 2, 2, 0, 0, 0, 0, 1 };
        public static int[] K = new int[] { 0, 0, 0, 2, 0, 1, 2, 2, 0, 1, 2, 0 };
        public static int[] L = new int[] { 0, 2, 0, 0, 2, 0 };
        public static int[] M = new int[] { 0, 0, 0, 2, 1, 1, 2, 2, 2, 0 };
        public static int[] N = new int[] { 0, 0, 0, 2, 2, 0, 2, 2 };
        public static int[] O = new int[] { 0, 0, 2, 0, 2, 2, 0, 2, 0, 0 };
        public static int[] P = new int[] { 0, 0, 0, 2, 2, 2, 2, 1, 0, 1 };
        public static int[] Q = new int[] { 1, 1, 2, 0, 2, 2, 0, 2, 0, 0, 2, 0 };
        public static int[] R = new int[] { 0, 0, 0, 2, 2, 2, 2, 1, 0, 1, 1, 1, 2, 0 };
        public static int[] S = new int[] { 0, 0, 2, 0, 2, 1, 0, 1, 0, 2, 2, 2 };
        public static int[] T = new int[] { 0, 2, 2, 2, 1, 2, 1, 0 };
        public static int[] U = new int[] { 0, 2, 0, 0, 2, 0, 2, 2 };
        public static int[] V = new int[] { 0, 2, 1, 0, 2, 2 };
        public static int[] W = new int[] { 0, 2, 0, 0, 1, 1, 2, 0, 2, 2 };
        public static int[] X = new int[] { 0, 0, 2, 2, 1, 1, 2, 0, 0, 2 };
        public static int[] Y = new int[] { 0, 2, 1, 1, 2, 2, 1, 1, 1, 0 };
        public static int[] Z = new int[] { 0, 2, 2, 2, 0, 0, 2, 0 };
        public static int[] zero = new int[] { 0, 0, 2, 0, 2, 2, 0, 2, 0, 0, 2, 2 };
        public static int[] one = new int[] { 0, 1, 1, 2, 1, 0, 0, 0, 2, 0 };
        public static int[] two = new int[] { 0, 2, 2, 2, 2, 1, 0, 1, 0, 0, 2, 0 };
        public static int[] three = new int[] { 0, 0, 2, 0, 2, 2, 0, 2, 2, 2, 2, 1, 1, 1 };
        public static int[] four = new int[] { 0, 2, 0, 1, 2, 1, 2, 2, 2, 0 };
        public static int[] five = new int[] { 2, 2, 0, 2, 0, 1, 2, 1, 2, 0, 0, 0 };
        public static int[] six = new int[] { 2, 2, 0, 2, 0, 0, 2, 0, 2, 1, 0, 1 };
        public static int[] seven = new int[] { 0, 2, 2, 2, 1, 0 };
        public static int[] eight = new int[] { 0, 1, 2, 1, 2, 0, 0, 0, 0, 2, 2, 2, 2, 1 };
        public static int[] nine = new int[] { 0, 0, 2, 0, 2, 2, 0, 2, 0, 1, 2, 1 };
    }
}

DebugTextTest.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

//sample usage of DebugText.cs
[ExecuteInEditMode]
public class DebugTest : MonoBehaviour {
	// Update is called once per frame
	[ExecuteInEditMode]
	void Update () {
		DebugText.Write("hello world", Vector3.zero, Color.red);
		DebugText.Write("YDIRECTION", Vector3.zero, Vector3.up, Vector3.forward, Color.green);
		DebugText.Write("ZDIRECTION", Vector3.zero, Vector3.forward, Vector3.left, Color.blue);
		Vector3 v = new Vector3(1,1,-1);
		DebugText.Write("MY DIRECTION", Vector3.zero, v, Vector3.Cross(v, Vector3.up), Color.blue);
	}
}