In this photo I have lined up a short selection of wire crimper's. The one on the far left IS NOT A CRIMPER! I only say this because I have witnessed people putting together marine terminations with a pair of PLIERS.
The next crimper, the one with the yellow handles, is a cheap hardware store quality crimper and should only ever be used in an absolute emergency.
The middle tool is a low grade Klein strip & crimp tool though it's not really well suited for much other than crimping non-insulated terminals and stripping wire.
The fourth tool is a good quality DIY grade crimp tool intended for heat shrink crimp terminals. This one is a CMI product & is a Taiwanese made version of the AMP 55893-1(LINK) tool and runs considerably less than half the cost. Sadly this AMP tool used to be made in the USA and apparently no longer is. Even FTZ, a tool I used to sell, that was made in Taiwan, is now "Made in China". The Taiwanese made crimp tools are generally considered a better quality than mainland Chinese tools are.
The CMI version is actually a better quality tool IMHO. This tool is designed specifically for crimping marine or aviation grade heat shrink terminals. The jaws of this crimper are fairly well machined, and wide enough in cross section, to produce a decent quality crimp. This crimper is also of the controlled cycle or ratcheting type and will not release until a proper crimp has been made.
The final crimper shown is another ratcheting type crimper but this one, set up with the jaws shown, is designed for insulated crimp terminals. It makes a "double crimp" for insulated terminals.
Read on for more details on these different crimpers.
NOTE: There is no such thing as a "marine grade" terminal. I refer to "marine grade" only because that is what the retailers tout them as and what most boaters know them as. "Marine Grade" is just a high quality insulated or heat shrink crimp termination. The same terminals are sold into aviation, industry and marine applications. In aviation they are often referred to as aviation grade... The difference with aviation terminals is that they need to meet minimum standards and be crimped with "certified" tools all of which are FAR MORE EXPENSIVE than the average boater is willing to buy. I personally & professionally use aviation certified tools but the ones below will get you you to better than average...