I'm looking for a good overdrive pedal that will tighten up my tone, give me a fair gain boost, with a mild colouring to the tone, but nothing too intense.

The trick here : No tubescreamers. They sound great, but they are absolutely not what I want. No Ibanez, no Maxon, no OCD.
I love my Keeley modded SD-1... you can try one out if they have them somewhere.
Marshall JCM 800 2205 Halfstack
Dunlop Crybaby
Keeley BOSS SD-1
MXR 10 band EQ
iSP Decimator
Menatone Blue Collar?

Strat, V847a, OCDv3, Carbon Copy, DD-5, Flying Dragon, EL84 amp
The Boss Blues Driver is a good pedal

Robert Keeley also makes a modded one if you're interested
Leader of The Cult of Echoes, for those who believe 23 min. of Pink Floyd Epicness just isn't enough.

Pm Alex the Red if you're interested

I'm a member I Pignose Amps Club. PM Woodenbanman if your interested.
Erm, a Boss OD-1 sounds like something you'd like. They're vintage though, so they're hard to find (although Ebay usually has a load). I have one, and I can tell you that it colours the tone slightly and has a load of gain. Really nice sounding!
Gonna Leave this town

Gotta leave this town

Gonna make a whole lotta money

Gonna be big yeah...
(Jimi Hendrix - Hear My Train A Comin')

Xotic RC booster or BB Preamp? How much gain are you looking for?
"The fool doth think he is wise, but the wiseman knows himself to be a fool." - W.S.
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Quote by Erock503
Xotic RC booster or BB Preamp? How much gain are you looking for?

Just a little bit, my amp covers most of the level of gain I need, but begins to, incidentally, lose tightness when it gets in the area. Then again, soon I'll be getting a small clean tube amp and I'll want something to drive it a little, so a reasonable amount of gain, then.