I've tried a lot of different basses, amps, cabs, fx etc over the years. These are some of my favourites...

Overwater Basses

Legendary UK luthiers. Most pro bass players I know own at least one Overwater bass. These guys really know how to make basses. Their standard models range from classic vintage designs to modern extended range instruments. Whatever you requirements they can advise you on choice of wood, hardware etc to build the right instrument for you. You can hear my Overwater basses on my classic bass sounds page here

Ampeg B15 'fliptop'.

  The B15 has been used on countless recordings over the past 50 years and still sounds fantastic.
This is a late 60s model. The earlier models have a slightly smaller cab size, in my opinion the larger cab size produces a fuller sound at higher gain settings.
In this picture I have the cab miked with a U87, you can hear it on the classic bass sounds page. Vintage B15s are too heavy and too valuable to take to gigs these days, but as a studio amp they are unbeatable!

Mark Bass SA450 Head

Mark Bass make fantastic gear - their heads and cabs are well constructed, amazingly light, and have transparent sound with some really useful controls. My favourite bit on this head is the VLE control (vintage loudspeaker emulator), I call it the 'old fashioned knob' - if I'm doing anything that sounds 'old skool' be it rock 'n' roll, jazz, soul or whatever - I dial in some of this and it gives me more of the character you get from vintage amps like the B15.
The  6x10 cab pictured here is the 106HF - I use this with an SA450 for my touring rig. The crew always love how light it is, and I love how it sounds.
The smaller heads and cabs all have the same characteristic warmth and transparency - can't recommend this gear highly enough!

Tech 21 SansAmp.

This preamp/DI box is one of those ridiculously useful bits of gear that every serious bassist should have in their toolbox. We all have many occasions where we DI our basses on gigs and in the studio, and often the result is a dry lifeless sound. The sansamp adds warmth and presence to the tone in a way that emulates the sound of a live rig. It can also be used as more of an FX pedal to add distortion. Applying distortion to a bass is fraught with danger. Many of the stomp boxes on the market will suck the life out of the sound and produce a thin bottom end. If you don't have the space or the budget to get into complex multi-channel set ups then this little box will give you a big fat dirty sound that's hard to beat.

Radial Tonebone PZ pre

This is a great pre-amp, designed for acoustic instruments. I use it with my double bass, it has some really useful features, particularly if you are playing at higher volumes where feedback can be an issue.
Double bass is a  notoriously difficult instrument to amplify well. There are booming low frequencies which you don't hear until you plug into an amp, hot spots that need taming in the middle frequencies, and when you play at higher volumes open strings will
often resonate and feedback if left unmuted for a second.
The PZ pre has a sweepable notch filter with 2 different settings and a phase reverse that usually sorts out feedback caused by the position of the bass in relation to the speaker. The eq section is only 4 band but the mid section is semi-parametric and very powerful. With double bass, eq-ing is really about cutting problem frequencies. I find that a very small change in the position of the mid cut on this pre-amp will make a big difference to the sound. With a bit of careful listening I can always find the sweet spot that gives me a great sound.

Boss LS2 line selector

Another amazingly useful bit of kit. There are many different combinations of ins and outs you van get with this little pedal. I've used it in several pedal board set ups. If you want to bypass all your other FX pedals (even with pedals that have true bypass you're still going through more patch cables and connections - more stuff to go wrong, right?), or if you want 2 different FX loops that you can switch between. Or send your signal to 2 different destinations (like 2 amps, or a stage rig and a DI). I'm currently using electric bass and double bass on the same gig, They go into separate pre-amps with their own DIs and I use the line selector to switch the send to my on stage rig.

Visual Sound Visual Volume Pedal

Your average volume pedal is ok for swells, or using as a mute switch, but it always used to frustrate me that you couldn't reliably set different volumes. I used to think "surely someone could make a pedal with increments from one to ten so you can set your volume to exactly the right level". And then a few years ago I found out that Visual Sound used to make a pedal that did that. It had been out of production for some years but they were relaunching it. So I bought one straight away, as did many other guitarists and bassists. Seems every pro player has one now - very useful for theatre stuff -  the dynamic range is huge on shows, underscore one minute - massive power ballad the next. And having the LED display makes it really easy to use in a dark pit or stage.