I'm going to try and keep this thread alive, as I believe it can be useful... but it needs more input.
Anyway, here are a couple more:
The ones I want to mention are the Rolson 4" square, a really excellent tool at well under £10. I use it more than any other adjustable square because it is the right size almost all the time, and it is very precise and solid. I did tweak it a tiny bit when I got it - wet'n'dry along the groove of the rule (so it slides better) and a dressing of the slightly rough casting where the lock-screw beds. this was all to make it smoother and faster to use, and it took minutes. But even out of the box it is really very good indeed. My U.S. Starrett is also good, maybe a tiny bit better*, but as the Starrett cost £60, the Rolson wins hands down (at around 13% of the price).
Also from Rolson, the 4" combi-square is equally good (the straight square is generally more useful). And the utility knife they do that folds... my absolute favourite utility knife. It is really nicely engineered. I found a box set of a wood handled version with a foldy multi-tool, all for about £18. They usually come with a blue anodised handle - if you see one around (about £6) get it! Their blades are really quite good too. Basically I recommend Rolson.
And the Japanese marking knife - v-tipped so fast to go left or right. Hyper-sharp, flat-backed... my favourite marker by far. About a tenner (Axminster). Oh yes, and I have used it many a time as a paring chisel too (inside joints).
On the older ebay stuff - the US Stanley 10 1/2 (the rebate plane) seems a luxury, but I found my first real use for it, cleaning the rebates for the woodscrews on the underside of the bench top.
The 10 1/2 isn't a budget tool (mine cost £85) but a reminder that old US Stanleys are brilliant - and you can pick up a No4 for around £35 - 40 (OK guys, knock a nought off at the bootfairs).
ON U.S. Stanleys, the 2" chisel shown has also been massively useful shifting waste in big joints (I bought 3 incl this on ebay for about £20).
And the mallet - that was free!... and you won't find one of those at the bootfair.
I will be adding to this - just a few things I use a lot, rate highly, and paid little for.
As Don Weber (reknowned bodger, blacksmith, maker and writer) said: " As with any craft you can spend a fortune just getting set up, or you can spend next to nothing and just get on with it."
*p.s. actually, no it isn't... not in any tangible way I could argue.