If you have a ZIII based Amiga (Amiga 3000's or 4000's), you should look at a Retina Z3, Cybervision 64, Cybervision 64/3d, or a Picasso IV. They are the fastest cards.
If you have a ZII bus (2000) - A Picasso II is a good choice. Others may have other ones as well.
If your into games the video card will be of very little use, very few games actually use the video cards and use OCS,ECS, or AGA.
If you want to make a really nice workbench, enjoy productivity software, surf the web, etc. You really need a video card for the best results.
Have fun...