The biggest was about 600-800 at St Andrews Uni in 1990 (I think, can't remember the exact year). It was OK but with the bright stage lighting, you couldn't see the audience. It was a bit like playing in front of a huge black curtain. It was cool to think of all the band that had been on that stage, Floyd, Zep, Hendrix, etc. (so I was told). James had played there just a few days before, they were massive in the UK at that time.
Smallest was 2 at a bar in Edinburgh, the couple that watches us loved it. They came up to us, after the gig, to buy CDs but at that time we didn't carry spares. So we took their address and mailed then one the next day, FOC, and someone made then a t-shirt too.
Worst gig was in Paisley, the only time I've ended a song and there was complete silence, not even polite applause. A horrible experience for any performer. They did clap for some of the latter songs but nothing went down well. At another gig, a well know local gangster said he would kill us if we were sh*t, I'm alive so I guess he liked us.