Shadowrun is, by design, a world where magic is feared and envied, and where technology is an ubiquitous presense that constantly tempts people with the promise of becoming more than human. Therefore, magic and augmentation can both augment a character's ability to superhuman levels at a comparatively cheap cost.
Mundanes are playable. But they are far, far from optimal. Be aware of that before you make one. They are more of an advanced roleplayer's choice, a decision to deliberately gimp your character to make the experience more challenging. The one tangible advantage that an unaugmented mundane has is the ability to pass through any magical or cybernetic scanner without breaking a sweat. They will also usually have more skills, but between skillwires, and all of the skill and Attribute boosts that are available, the augmented character with three initiative passes and several Attributes boosted up to 9 might actually have more skills/higher dice pools than his unaugmented counterpart, too.
An unaugmented mundane will be second-best at anything he does, but can still do a decent job at some specialties. Generally, a mundane character will depend on stealth, cunning, and setting the terms of the confrontation to survive. They can be acceptable snipers, hackers, faces, detectives, and techies.
Here's one quick example:
Face
Race: Elven
BREAKDOWN (400 Points)
Core Attributes: 200
Special Attributes: 40
Race: 30
Active Skills: 140
Qualities: +30
Contacts: 10
Resources: 10
=Attributes=
Body: 3
Agility: 4
Reaction: 3
Strength: 2
Charisma: 7
Intuition: 4
Logic: 3
Willpower: 5
Edge: 5
Essence: 6.0
=Qualities=
First Impression
---------------
Allergy/Silver, Moderate
Low Pain Tolerance
Sensitive System
=Active Skills=
Gymnastics/Dance: 4/+2
Influence Group: 4
Intimidation: 4
Perception/Visual: 4/+2
Pistols/Semi-Automatic: 4/+2
Stealth Skill Group: 3
=Knowledge Skills=
English: N
Japanese: 4
Sperethiel: 4
--------------
Local Area Knowledge: 4
Psychology: 3
Seattle Night Spots: 3
Street crime/Vice: 2/+2
=Contacts=
Fixer (4 Connection/2 Loyalty)
Hacker (2 Connection/2 Loyalty)
=Lifestyle and Gear=
50,000 Nuyen to spend on Lifestyles and Gear.