With smartphones all looking very similar these days, you might think there's a lull in design innovation.

Cast your mind back over the past decade-and-a-half and experimentation and innovation were running wild, with phone makers looking to create the next hit product.

This led to odd-shaped mobiles with very interesting features. CNBC spoke to an avid collector of old phones Ben Wood, the chief of research at CCS Insight.

Wood helped CNBC compile a list of some of the weirdest and wackiest phone designs ever, as the Mobile World Congress (MWC) kicks off in Barcelona.

Is it a pen? Is it a phone? Well it can't write anything, but it can make calls.

Not only did it have a tiny screen but also a little camera, all packed within a thin pen-like body.

The Haier P7 also had a battery that could give 3 hours talk time.

Aimed at the fashionable cool kids, Nokia's teardrop-shaped device was very unique.

The small screen in the middle was surrounded by buttons which made it difficult to use with one hand.

It did however connect to 3G internet and boasted a 0.3 megapixel camera.

Nokia's thin phone was dubbed the "Lipstick Phone" and was aimed at fashion-forward and young consumers.

"Perfect to whip out at cocktails, the Nokia 7280 is geared to attract attention and become the talking point at any high glamour soiree," Nokia said in a press release at a time.

There was no keypad but instead Nokia put a dial on the phone for people to navigate.

The N-Gage was Nokia's attempt to merge a handheld games console and mobile phone.

It was a time when Nintendo dominated the handheld games market and Nokia attempted to steal users from the Japanese giant.

The N-Gage featured a 2.1 inch screen with buttons along both sides of its elongated form.

Siemens modeled the Xelibri 6 on a make-up powder container with a mirror in a bid to tap into female users.

Like many of the phones at the time, Siemens was trying to position its device as a fashionable item for youngsters, describing the handset as combining "extremes from the world of fashion and mobile phone technology."

"Two integrated mirrors - one with a magnifying effect - make the Xelibri 6 a practical and, at just under 90 grams, very wearable accessory for carrying in any purse or pocketbook," Siemens said in a press release at the time.

The Xelibri 6 was available in "sheer bronze" and "platinum blush" color variants, with Siemens describing it as "this season's most unusual snap-shut mobile."

Nokia continued to push the boundaries when it came to design and the N90 was all about the rise of camera phones.

The device was able to twist and swivel into a shape that resembled a handheld video camera. It had a 2-megapixel camera with 20 times digital zoom, flash and on-phone editing capabilities.

"We foresee that already this year, the camera phone market will grow to be over four times the size of the digital camera market," Nokia said in a 2005 press release, highlighting the bets the company was making on camera technology.

The Motorola MPx was a "dual hinge" handset which meant it opened vertically like a traditionally flip phone, but also horizontally to reveal a QWERTY keyboard.

Motorola marketed this as a phone for "mobile professionals", with a 2.8 inch, 16-bit color display, running Microsoft Windows Mobile software. It boasted a 1.3 megapixel camera and Motorola emphasized the email and productivity capabilities of the device. The MPx also came with a stylus.

"This revolutionary compact form factor combines powerful hardware and software enablers and Microsoft's Windows Mobile software, to create a true mobile assistant – helping mobile professionals stay ahead of the curve," Motorola said in a press release at the time.

Nokia marketed the 3650 as a multimedia phone with its camera, color display and round keypad.

The handset supported multimedia messaging service (MMS) which let consumers send picture and sound messages to each other. This was before the days of internet-based services like WhatsApp.

"The Nokia 3650 is the next must-have device that defines what an imaging phone must do," Nokia said in a press release at the time.

The Voq Professional Phone was aimed at business users with the main attraction being a flip open QWERTY keyboard.

It ran Windows Mobile but had no camera.

LG's recent bid to make a comeback in the smartphone market saw it release a "modular" smartphone in the form of the G5.

It allowed users to replace parts of the phone such as the battery and add accessories. The LG G5 was not a huge hit for LG, but it showed the company could still innovate in the market.

More an entertainment device than a mobile phone, the Nokia 5510 had an elongated shape with a screen in the middle and keys either side.

Users had to turn the phone sideways in order to talk on a phone call.

"Every now and then it is crucial that you turn your thinking around. This time we took a phone, turned it sideways, added a full keyboard, music, and some fun. This new concept reflects not only a change in our perspective, but also a more fundamental transition that our industry is going through," Nokia said in a press release at the time.

"Phones are no longer only voice and sms driven, but are increasingly functioning as platforms for other services, such as entertainment," the company added, hinting many years ago what modern day smartphones have become.