The Elder Scrolls V: Skyrim Glitches

Early Level Up Exploit
Just after the Character Creation and the following of either the Imperial or Stormcloak (either choice doesn't matter), you real a point where there you'll find a sleeping Bear to sneak past or attack. You can attack your companion NPC without them retaliating. This is good for working on your One-Handed, Two-Handed, Sneak, Spells and Blocking and Levelling.