It helps you to be prepared in any situation.
However, not all survival knives are created equal.
Each will come with different material and features to serve different purposes.
It requires an appropriate knowledge so you can choose the right knife that fit your need perfectly.
Choosing Your Best Survival Knife
Folding blade is easy to carry on a day-to-day basis but since it made of two pieces joined by a hinge, the chances to break off are much higher.
While fixed blade is very versatile and reliable. It will serve you much better in a survival situation. 
Stainless steel blade is virtually indestructible, can take a beating, and last a long time without rusting. However, many survivalists say stainless blades lose an edge faster than carbon.
While carbon is usually known to hold a good edge longer than stainless steel, but will rust faster.
Straight blade - work better for chopping wood and is much easier to sharpen. A good smooth stone can even be used to sharpen it.
While serrated blade will require a special knife sharpener.
C. Length & Thickness
Any knife which is less than 6 to 12 inches might not be big enough to do the things you will have to get done in a survival situation.
3/16 -4/16 of an inch thickness is the best for survival knives because it will be extremely solid and able withstand the abuse of wood chopping and prying. 
• Double-edged spear point and tanto-style knives - are built for fighting and perfect for thrusting and stabbing, but do not hold out well in a survival situation.
• Clip point or a drop point are suited well for various tasks required in a survival situation.
However, please be advised that clip points with exaggerated curves are susceptible to breakage if your pounding the spine while chopping wood. 
• Wood and bone handles can be very comfortable and wear nicely, but are prone to cracking or drying out if not cared for.
• Metal (steel or aluminum) is strong and long-lasting, but can be heavy and gets hot or cold depending on the conditions.
• Rubber can be comfortable if designed properly and absorbs vibration, but can deteriorate or get damaged more easily. 
5. Other Features To Consider:
• Full tang - it can`t break off easily.
• Flat spine - better for batoning and striking flint to get a spark.
6. What Other Users Have Said
There is a great advantage if you buy your survival knife online is that you can see directly the opinions of other users.
And that is why large and trusted online retailer like Amazon.com displaying their customer reviews including the star rating. It will give you a real picture of a product you plan to buy.
The more the number of buyer reviews and the higher the star rating, the better the product in the eyes of consumers.
For your information, people who can submit a product review on Amazon.com must make the purchase first. So rest assured, you will get an honest review from them.
Now, get yours!!!
Top 10 Best Survival Knives
1. TAC Force TF-705RB (under $13)
• Reviewed by 5,204 verified buyers - 4.5 out of 5 stars - READ REVIEWS
• Spring assist folding knife offers rapid one-handed deployment, locks securely into place with liner lock
• Black half-serrated stainless steel blade
• Aluminum handle with bottle opener and glass breaker for emergencies
• Comes complete with a pocket clip for easy and safe carry
• 4-1/2-inch closed length, 3-1/4-inch blade length with 3mm thickness
2. SE KHK6320 Tanto Knife (under $7)
• Reviewed by 2,929 verified buyers - 4.1 out of 5 stars - READ REVIEWS
• Full tang fixed blade outdoor knife for rugged camping expeditions
• Black stainless steel tanto blade
• Cord-wrapped handle provides superior grip, plus handy cording when needed in a pinch
• Nylon sheath for easy and safe carry; magnesium alloy fire starter enables you to effortlessly start a fire in no time
• 7-inch overall length, 3-inch blade length with 4mm thickness
3. BlizeTec (under $39)
• Reviewed by 1,605 verified buyers - 4.5 out of 5 stars - READ REVIEWS
• Premium 5-in-1 pocket-size stainless steel foldable survival knife with nylon pouch.
• Drop-point blade with serrated saw, bright LED flashlight, magnesium alloy fire starter, blade lock, window breaker, seatbelt cutter and pocket clip.
• Weighs only 5.46oz.
• The entire knife including handle is 8.5 inches long when open.
• Flexible carry options with the included nylon pouch, belt clip.
• Lifetime warranty.
4. Smith & Wesson SWBG2TS (under $20)
• Reviewed by 1,549 verified buyers - 4.4 out of 5 stars - READ REVIEWS
• Folding Knife
• 40% Serrated Tanto Blade
• Lifetime Warranty
• Dimensions: 6 x 6 x 4.5 inches, 10.4 ounces
5. KA-BAR 1217 (under $68)
• Reviewed by 1,496 verified buyers - 4.9 out of 5 stars - READ REVIEWS
• Full Size US Marine Corps Fighting Knife
• 100% Leather Sheath
• 1095 Cro-van steel
• 7" Straight Edge Blade
• Leather Handle, USMC Fightning Knife
• Dimensions: 13.5 x 3 x 2.5 inches ; 11.2 ounces
6. Gerber Bear Grylls(under $33)
• Reviewed by 1,419 verified buyers - 4.6 out of 5 stars - READ REVIEWS
• Molded rubber grip and knurled striking surface butt cap
• Saw ground back blade
• Integrated fire starter with integrated diamond sharpener
• Key ground-air communication patch
• Emergency micro lanyard whistle
• Overall length: 10".Weight: 11.2 oz
7. Morakniv Companion (under $25)
• Reviewed by 1,400 verified buyers - 4.9 out of 5 stars - READ REVIEWS
• Fixed blade knife with a stainless steel blade
• Patterned high-friction grip handle
• Plastic sheath with a belt clip
• Black powder coat finish for non-reflective applications and extra corrosion resistance
• Blade Thickness: 2.5 mm, Blade Length: 104 mm, Total Length: 224 mm
• Also available in assorted colors
8. Ka-Bar Becker BK2 (under $83)
• Reviewed by 1,336 verified buyers - 4.7 out of 5 stars - READ REVIEWS
• Full tang heavy duty field knife suited for camping chores.
• Drop point blade shape
• 20-degree blade angle
• Comes with a hard shell black nylon sheath.
• Dimensions: 18 x 5 x 5 inches ; 1 pounds
9. Gerber LMF II (under $78)
• Reviewed by 1,050 verified buyers - 4.7 out of 5 stars - READ REVIEWS
• Rugged, versatile survival tool
• Safety knife included
• Low-profile sheath with built-in sharpener
• Sheath Material: Ballistic nylon with fire retardant coating
• Handle Material: Glass-filled nylon with TPV overmold
• Lifetime warranty
• Dimensions: 16 x 8 x 4 inches, 2.1 pounds
10. Schrade SCHF9 (under $39)
• Reviewed by 1,041 verified buyers - 4.6 out of 5 stars - READ REVIEWS
• 6.4" fixed blade, 5.6" handle
• 1095 High Carbon Steel
• Kraton handle
• 15.9 ounces
• Includes nylon sheath
• Lifetime Warranty