How Can the Pressure be Increased in a Shower?

If the shower is fed from a hot water tank, a cold water tank provides the pressure head to force out the hot water from the tank. This is usually in the loft to maximize the head so if it is located there, you are not going to be able to rise it any higher.
Cold water power showers are fed from the incoming mains cold water supply and the water is heated by a high powered electric element.
Shower heads incorporate a restrictor/aerator to reduce flow and water wastage. The Federal Energy Policy Act of 1992 made it a requirement that these were added to shower heads to reduce flow to about 2 gallons per minute, so removing this would increase the flow rate. Also it is possible to buy a shower head designed for a lower flow rate. This increases pressure but the flow rate will be less.
You can buy a booster pump which effectively works like a power washer and increases the pressure while keeping the flow rate constant.

How Can Hand or Garden Tools be De-Rusted?

Remove excess rust with steel (wire) wool soaked in lemon juice or vinegar which are mild acids. Rinse the tools and allow them to dry. You could soak the tools for a period to remove excess rust.
Another alternative which definitely works is phosphoric acid. This is often a constituent of rust removing chemicals and can also be bought in gallon containers from companies which supply cleaning chemicals. It is a powerful acid and can also be used for removing limescale from surfaces. Usually it is diluted with water before use. The objects being cleaned are submerged in the solution and should only be left in the acid for the bare minimum of time to dissolve the rust, otherwise the acid will start to dissolve the underlying metal! I have cleaned an old vice pillar drill vice belonging to my grandfather which developed a thick layer of rust after being exposed to dampness in a shed for over thirty years and the acid completely removed the rust.
Once you remove the rust, rub some oil into them and wipe off any excess. This will help to prevent future corrosion.
Sand can also be used as an abrasive for removing rust from tools.
If you wipe tools with light oil after use, it helps to prevent condensation and subsequent corrosion. Guns and tools were traditionally given (and probably still are) a coating of oil after manufacture and before packing to protect them from dampness and rust.

What Does the Voltage Rating of a Fuse Mean?

Image Courtesy, mtself CC BY SA 3.0 via Wikimedia Commons

The current rating of a fuse specifies the current which the fuse will carry without blowing. Once the current exceeds this value, the fuse will eventually blow. The characteristic of a fuse is such that if the current in a circuit is moderately higher than the fuse rating due to an overload, the fuse will take some time to blow, possibly seconds, minutes or tens of minutes, depending on the magnitude of the overload. If the current is a lot higher e.g. in the case of a short circuit, the fuse will blow in a few tens of milliseconds. While a low voltage or high voltage fuse will blow when the current exceeds the current rating, the current flow in a mains powered circuit can be extremely high (possibly thousands of amps) in a short circuit scenario because the current is coming from a large transformer outside the home. The breaking capacity of a fuse is specified in joules or kiloamps and a mains fuse could have a rating of 10000 amps or more. This is the maximum current the fuse can carry without rupturing. Usually fuses for mains equipment or distribution circuits have a ceramic body to withstand the heat and shock when the fuse blows. The fuse is also filled with quartz sand to absorb the heat and shock and quench the arc when the fuse blows. A glass fuse could simply rupture and possibly cause a fire if it carried such a heavy current. Glass/low voltage fuses may be used on the secondary side of the transformer in the power supply of equipment because the current output of the transformer in a short circuit situation is limited.

Good DIY Gifts For Men?

I better be diplomatic about this and suggest that DIY gifts for men needn't be any different than those which would be suitable for all the ladies amongst us (and even "non-ladies"!) Speaking as a serious male DIYer, I would like a cordless drill with two lithium batteries. The advantage of this battery technology is that the batteries don't lose their charge as quickly, and the drill is always ready for use.
A mitre(miter) saw is useful for making square cuts on timber, dado rail etc. An 8inch version is fine.
Jigsaws are useful for making curved and straight cuts in sheet timber. Go for one with variable speed on the trigger.
Angle grinders are useful for cutting metal and masonry.
A socket wrench set or ratchet wrenches(spanners) are always handy for tightening and undoing nuts and bolts.
Personally I would prefer to buy my own hand tools. While power tools are somewhat similar, the shape and size of hand tools are such that it is better to try them in your hand before buying. I mean how would a woman feel if their partner bought them shoes?