Crow Road from Lennoxtown over Campsies and Tak Ma Doon Road from Kilsyth over Campsies are two of the longest in that area. Plenty of short sharp climbs in the actual city, e.g Gardner Street in Partick, Montrose Street near Strathclyde Uni. On the south side, there's Gleniffer Braes from Paisley, Ferenze Road from Neilston, Bonnyton Moor Road from Waterfoot, Eaglesham Moor Rd, Ardochrig Road Auldhouse, Darvel Mast Climb at Priestland. Also plenty of climbing around the Clyde Valley/Braidwood/Lanark area. Further afield there's the Menock Pass in the Leadhills, Beef Tubs at Moffet etc.
Depends how you define tough. Short and steep, I'd add Montrose St from George St to Cathedral St (part of the Commonwealth Games RR circuit) and Scott St (off Sauchiehall St up to the art school).
Longer: the East Kilbride Rd from Burnside Rd towards EK (I once measured it as almost exactly 2 miles) and Carmunock Rd from Kings park up to Carmunock (haven't measured it, but probably 1-1.5 miles).