I've 'done' all the Messiers - apart from a handful that are at too low a declination to see from my location (54.6°N, in UK)
Going to Southern Portugal next year, and plan to pick up the last few while there.

Equipment-wise - I've observed most of them many times, through various bits of kit - Binoculars, 4" apo-refractor, 6" EQ-newtonian, and 10" Dobsonian.
Faves are probably m57 (ring neb), m27 (dumbell), m31 (Andromeda Galaxy) - the pairing of m81 and m82 (Bode's and the cigar galaxies) are particularly nice in the same widefield view.
m13 (Hercules globular cluster) is fantastic in a big reflector.
I'm also a big fan of open clusters - m44 (beehive) is lovely in binocs from a proper dark-sky site.
The little chain of m37, m36, m38 open clusters up through Auriga are good - and look for the 'smiley=face' asterism of stars to the right of m38 (widefield binoc view)
Could go on and on, but don't wanna bore people - but a few no-Messier objects that are also great IMHO....
Perseus Double-Cluster (ngc869 and ngc884) - like two little clusters of diamonds on black velvet
ngc457 - the 'Owl' cluster (aka 'ET' cluster in USA) - in Cassiopeia. It actually does look like an owl.
Collinder 399 (coathanger cluster) - a very loose open cluster, of which the brightest stars appear in the shape of a dot-to-dot coathanger - in Vulpecula, between Cygnus and Aquila
ngc7789 - Herschell's spiral cluster - a faint-ish open cluster in Cassiopeia - with a good dark site, and just the right size scope, there appears to be a spiral structure to the cluster - it isn't really there though, just an effect you get under the right conditions - too small a scope, and you can't see the effect, too big, and you gather too much light and detail, and the effect is lost. 6" to 8" will show the effect under a good sky - 10" to 12" required if you have significant light pollution at your viewing site.