Fuses/breakers are safety items, so don't forget that. They prevent fires/loss of equipment, and possible human damage. Certified or not, that's an area where price shouldn't over ride purpose.
I don't like the automotive fuse blocks as they retain the fuses by friction fit. World wide, glass fuses are easier to find than the blade types. I use breakers, whether certified or experimental, as the styles I use are relatively sealed and have a good track record. Also be sure not to use the non resettable breakers. If one trips during a flight, you might just need to force the reset to keep a function (think fuel transfer pump with no place to land).
When I do use fuses, I favor a water resistant type (Bulgin FX0180). Simple to install on an existing wire and stays intact when installed.
Web
Ordinarily, I would not presume to disagree with Web... His expertise and advise in this forum has been invaluable to me. But in this case, I do take exception with him on one narrow point: Those "automotive fuse blocks" are used (almost exclusively) in off-road racing, dirt bikes, and offshore racing power boats, where they are subjected to more vibration and stress than they would ever encounter in a light plane. If the "friction fit" retention was a problem, it would show up in that environment far sooner than it would in light planes.
The auto (and boating) world has pretty much moved away from "glass fuses" for the vast majority of applications (other than the occasional in-line add-on circuits). I believe you could go into pretty much any auto parts store in the world and be able to find those blade-type fuses... After all, if that country has autos on the road that were built after about 2000 or so, they're almost certainly using blade-type fuses, and thus the parts places will have them in stock.
OK - having disposed of that minor disagreement... The US Army used to have a "standard operating procedure" concerning circuit breakers... If they popped in flight, you could reset them ONCE, and once only. If they popped again, resetting was prohibited until maintenance had been performed to determine the root cause of the problem. I feel the same way about fuses – if they "fried" themselves protecting the circuit, I don't want to re-connect that circuit until I understand why it happened.
And I sure don't want to be doing that troubleshooting in the air, unless (as Web correctly points out) the design of the system in question left me no other alternative in an emergency-type situation. And here's one invaluable piece of knowledge I acquired from Bob Nuckols' "AeroElectric Connection" book and online forum: Design for simplicity, but include redundancy where essential. In the case of a fuel transfer pump as a single point of failure, it might be worthwhile to have a secondary transfer pump as a backup – on a completely separate electrical circuit, of course.
The question then becomes, is the additional weight and complexity of the backup system justified by the risk of a single point of failure? Flying in Texas, Oklahoma, and Kansas, I might say that secondary fuel transfer pump was overkill, because reasonably "survivable" places to land are abundant.
On the other hand, when flying over Canyonlands National Park recently – often going 5-10 minutes at a time where there was absolutely no place to land without destroying the airplane – I was
acutely aware that my RANS S-6ES has only the engine-driven fuel pump (no electric backup) and that if it should fail, I'd be in a world of hurt... My thinking on this was probably colored by the fact that two days earlier, I was flying with a friend in his Cherokee 160 when his engine sputtered and died. Turning the electric fuel pump on restored power instantly. Turns out the engine-driven fuel pump had failed. That thought was going through my mind during the flight over that beautiful, but ultimately hostile to landing aircraft terrain.
Thus, I will be adding an electric backup pump to my plane in the near future. And I'll probably use a circuit breaker on that circuit, for the reasons Web articulated in his post. (And, yes, it's nice to be flying an Experimental, where I've got the choice to alter the system to meet my needs...)