One problem w/ firearms vs. zombies is the limited amount of ammunition. For guns, the shotgun seems to be the obvious choice, but for long term survival, here's my strategy:
1. A long bladed weapon that can kill from outside arms reach.
2. Something for killing the ones that get into that perimeter.
3. This is the most important: Control your engagements so that you can't be overwhelmed. Don't get boxed into a corner, and set it up so that you can control how many zombies are immediately dangerous. An open field, don't let yourself get flanked, don't always wait for them, pick them off as fast as you can on a one to one basis without getting enveloped. Zombies have poor strategy, they rely on numbers. So if you wittle away at them effectively, you might be able to stay alive. You just need to kill all of the ones that know where you are before you're overcome with fatigue, or have an exit strategy that can take you out of their reach for rest.
Also, a problem w/ cars and RVs: fuel. A bicycle isn't sexy, but it's fast enough (zombies are slow) and isn't dependent on infrastructure to the same degree as a motor vehicle.