We've said it before, and we'll say it again... When choosing your dive knife, you need to decide if you want a convenient tool for emergency use, or are you needing a larger blade for heavy duty use?
If it's the first option, then the Pro Dive BCD Knife is a solid choice. This knife fits securely to your BCD with the included clip or lanyard, or you can also mount it to a low pressure hose on your regs. One of our favourite mounting spots is on your inflator hose - it's easy to get to with either hand, and if you've forgotten your knife then it means you've likely forgotten your regs too (which is usually easy to spot)!
This BCD knife comes in 'pointy' or 'blunt' versions depending on your needs.
*1 knife included, multiples shown to illustrate